Search space configurations for random access messaging

ABSTRACT

Methods, systems, and devices for wireless communications are described. In some systems, a user equipment (UE) may perform a random access (RACH) procedure based on a selected synchronization signal block (SSB). During this RACH procedure, a base station may transmit physical downlink control channel (PDCCH) messages for UE RACH message handling. To receive PDCCH signaling for RACH Messages 2, 3, or 4 (Msg 2/3/4), the UE may identify a set of time resources used by the base station for transmitting SSBs that are not quasi-co-located (QCL) with the selected SSB. The UE may identify a Msg 2/3/4 search space that does not overlap with this identified set of resources, and may monitor this identified search space. The search space may correspond to a modified remaining minimum system information (RMSI) search space indicated by the base station, or a valid RMSI search space not indicated by the base station.

CROSS REFERENCES

The present application for patent claims the benefit of U.S.Provisional Patent Application No. 62/659,616 by Islam et al., entitled“SEARCH SPACE CONFIGURATIONS FOR RANDOM ACCESS MESSAGING,” filed Apr.18, 2018, assigned to the assignee hereof, and expressly incorporated byreference in its entirety herein.

BACKGROUND

The following relates generally to wireless communications, and morespecifically to search space configurations for random access (RACH)messaging.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform-spread-orthogonal frequency division multiplexing(DFT-S-OFDM). A wireless multiple-access communications system mayinclude a number of base stations or network access nodes, eachsimultaneously supporting communication for multiple communicationdevices, which may be otherwise known as user equipment (UE).

In some wireless communications systems, a UE may perform a RACHprocedure with a base station to gain access to the wireless network.This RACH procedure may include the communication of a number ofmessages between the UE and base station, including RACH message 1(Msg1), message 2 (Msg2), message 3 (Msg3), and message 4 (Msg4)transmissions. RACH Msg1 may include a RACH preamble transmission fromthe UE to the base station, RACH Msg2 may include a random accessresponse (RAR) message transmitted in response, RACH Msg3 may include aradio resource control (RRC) connection request transmitted from the UEto the base station, and RACH Msg4 may include a medium access control(MAC) control element (CE) for contention resolution transmitted by thebase station in response. Each of these RACH messages may be associatedwith information transmitted by the base station on the downlink (e.g.,scheduling grants transmitted as physical downlink control channel(PDCCH) transmissions). However, the UE may not be able to efficientlydetermine resources on which to receive these PDCCH transmissionswithout interrupting reception of other transmissions (e.g.,synchronization signaling).

SUMMARY

The described techniques relate to improved methods, systems, devices,or apparatuses that support search space configurations for randomaccess (RACH) messaging. Generally, the described techniques provide fora user equipment (UE) to perform a RACH procedure while maintaining thecapability to receive non-quasi-co-located (QCL) transmissions. The UEmay initiate the RACH procedure with a base station based on a selectedsynchronization signal block (SSB). During this RACH procedure, the basestation may transmit physical downlink control channel (PDCCH) messagesto the UE for RACH message handling (e.g., scheduling). To receive thePDCCH signaling for RACH Messages 2, 3, or 4 (Msg 2/3/4), the UE mayidentify a set of time resources used by the base station fortransmitting SSBs that are not QCL with the selected SSB. The UE mayidentify a Msg 2/3/4 search space that does not overlap with thisidentified set of resources, and may monitor the identified searchspace. In some cases, the Msg 2/3/4 search space may correspond to amodified remaining minimum system information (RMSI) search spaceindicated by the base station (e.g., modified by removing resourcesconflicting in time with the non-QCL SSBs), or a valid RMSI search spacenot indicated by the base station (e.g., where the resources of thevalid RMSI search space do not conflict in time with the non-QCL SSBs).As a result, the UE may receive a configuration for the Msg 2/3/4 searchspace, and may remove resources from the configured search space thatoverlap in time with the non-QCL SSBs. The UE may receive the PDCCHtransmissions and the non-QCL SSBs from the base station based on thedesign of the identified search space.

A method for wireless communications at a UE is described. The methodmay include transmitting, to a base station, a first RACH message basedon an SSB received by the UE on a first receive beam, identifying a setof time resources used by the base station for transmission of one ormore other SSBs from the base station, identifying a search space forreceiving a PDCCH message based on the first RACH message, where theidentified search space includes time resources that are different fromthe identified set of time resources, and monitoring for the PDCCHmessage in the identified search space.

An apparatus for wireless communications at a UE is described. Theapparatus may include means for transmitting, to a base station, a firstRACH message based on an SSB received by the UE on a first receive beam,means for identifying a set of time resources used by the base stationfor transmission of one or more other SSBs from the base station, meansfor identifying a search space for receiving a PDCCH message based onthe first RACH message, where the identified search space includes timeresources that are different from the identified set of time resources,and means for monitoring for the PDCCH message in the identified searchspace.

Another apparatus for wireless communications at a UE is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable to cause the processor to transmit, to abase station, a first RACH message based on an SSB received by the UE ona first receive beam, identify a set of time resources used by the basestation for transmission of one or more other SSBs from the basestation, identify a search space for receiving a PDCCH message based onthe first RACH message, where the identified search space includes timeresources that are different from the identified set of time resources,and monitor for the PDCCH message in the identified search space.

A non-transitory computer-readable medium for wireless communications ata UE is described. The non-transitory computer-readable medium mayinclude instructions operable to cause a processor to transmit, to abase station, a first RACH message based on an SSB received by the UE ona first receive beam, identify a set of time resources used by the basestation for transmission of one or more other SSBs from the basestation, identify a search space for receiving a PDCCH message based onthe first RACH message, where the identified search space includes timeresources that are different from the identified set of time resources,and monitor for the PDCCH message in the identified search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the PDCCH message includes aPDCCH grant for a RACH message 2 (Msg2) transmission, a PDCCH grant fora RACH message 3 (Msg3) transmission, a PDCCH grant for a RACH message 4(Msg4) transmission, or a combination thereof.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the one or more other SSBsmay be received by the UE on receive beams that may be different fromthe first receive beam.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for identifying an RMSI search spacecorresponding to the SSB and configured via a physical broadcast channel(PBCH) configuration.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, identifying the search spacefurther includes removing time resources from the identified RMSI searchspace that overlap with the identified set of time resources, where theidentified search space includes remaining time resources of theidentified RMSI search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, removing the time resourcesfor the identified RMSI search space includes altering a slot-levelperiodicity of the identified RMSI search space, where the identifiedsearch space includes same symbol index locations as the identified RMSIsearch space but with the altered slot-level periodicity of theidentified RMSI search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, identifying the search spacefurther includes determining to implement a default search space basedon an RMSI transmission from the base station. Some examples of themethod, apparatus, and non-transitory computer-readable medium describedherein may further include processes, features, means, or instructionsfor identifying monitoring occasions for monitoring for the PDCCHmessage based on monitoring occasions of the RMSI search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, identifying the search spacefurther includes identifying an RMSI search space with time resourcesnon-overlapping with the identified set of time resources, where theidentified search space includes the identified RMSI search space.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for receiving, from the base station,an indication of a set of time resources for the search space. Someexamples of the method, apparatus, and non-transitory computer-readablemedium described herein may further include processes, features, means,or instructions for removing time resources of the identified set oftime resources from the indicated set of time resources for the searchspace, where the identified search space includes remaining timeresources of the indicated set of time resources for the search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the indication of the set oftime resources for the search space includes a time window for thesearch space. In some examples of the method, apparatus, andnon-transitory computer-readable medium described herein, a subset ofslots of the time window include the identified search space. In someexamples of the method, apparatus, and non-transitory computer-readablemedium described herein, the subset of slots includes each slot of thetime window.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, identifying the search spacefurther includes identifying a start of the search space based ontransmitting the first RACH message and identifying an end of the searchspace based on a response timer. In some examples of the method,apparatus, and non-transitory computer-readable medium described herein,the response timer includes a random access response (RAR) window, acontention resolution timer, or a combination thereof.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for receiving the SSB from the basestation, where the first RACH message may be transmitted in a RACHoccasion corresponding to the SSB.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for selecting the first receive beam,where the identified search space may be monitored using the selectedfirst receive beam during the time resources that may be different fromthe identified set of time resources. Some examples of the method,apparatus, and non-transitory computer-readable medium described hereinmay further include processes, features, means, or instructions forselecting a second receive beam different from the selected firstreceive beam. Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for monitoring for at least one SSB ofthe one or more other SSBs using the selected second receive beam duringthe identified set of time resources.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for receiving the at least one SSB ofthe one or more other SSBs from the base station based on the timeresources for the identified search space not overlapping with theidentified set of time resources.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for receiving the PDCCH message incontrol channel elements (CCEs) of the identified search space based onthe monitoring.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the one or more other SSBsinclude one or more SSBs actually transmitted by the base station.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for receiving, from the base station,an indication of the one or more SSBs actually transmitted by the basestation in RMSI, other system information (OSI), a radio resourcecontrol (RRC) message, a medium access control (MAC) control element(CE), a handover message, or a combination thereof.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, locations of the one or moreother SSBs may be fixed.

A method for wireless communications at a base station is described. Themethod may include receiving, from a UE, a first RACH message based onan SSB received by the UE on a first receive beam, identifying a set oftime resources used for transmission of one or more other SSBs by thebase station, identifying a search space for the UE to receive a PDCCHmessage based on the first RACH message, where the identified searchspace includes time resources that are different from the identified setof time resources, mapping the PDCCH message to CCEs within theidentified search space, and transmitting, to the UE, the PDCCH messageaccording to the mapping.

An apparatus for wireless communications at a base station is described.The apparatus may include means for receiving, from a UE, a first RACHmessage based on an SSB received by the UE on a first receive beam,means for identifying a set of time resources used for transmission ofone or more other SSBs by the base station, means for identifying asearch space for the UE to receive a PDCCH message based on the firstRACH message, where the identified search space includes time resourcesthat are different from the identified set of time resources, means formapping the PDCCH message to CCEs within the identified search space,and means for transmitting, to the UE, the PDCCH message according tothe mapping.

Another apparatus for wireless communications at a base station isdescribed. The apparatus may include a processor, memory in electroniccommunication with the processor, and instructions stored in the memory.The instructions may be operable to cause the processor to receive, froma UE, a first RACH message based on an SSB received by the UE on a firstreceive beam, identify a set of time resources used for transmission ofone or more other SSBs by the base station, identify a search space forthe UE to receive a PDCCH message based on the first RACH message, wherethe identified search space includes time resources that are differentfrom the identified set of time resources, map the PDCCH message to CCEswithin the identified search space, and transmit, to the UE, the PDCCHmessage according to the mapping.

A non-transitory computer-readable medium for wireless communications ata base station is described. The non-transitory computer-readable mediummay include instructions operable to cause a processor to receive, froma UE, a first RACH message based on an SSB received by the UE on a firstreceive beam, identify a set of time resources used for transmission ofone or more other SSBs by the base station, identify a search space forthe UE to receive a PDCCH message based on the first RACH message, wherethe identified search space includes time resources that are differentfrom the identified set of time resources, map the PDCCH message to CCEswithin the identified search space, and transmit, to the UE, the PDCCHmessage according to the mapping.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the PDCCH message includes aPDCCH grant for a RACH Msg2 transmission, a PDCCH grant for a RACH Msg3transmission, a PDCCH grant for a RACH Msg4 transmission, or acombination thereof.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the one or more other SSBsmay be received by the UE on receive beams that may be different fromthe first receive beam.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for identifying an RMSI search spacecorresponding to the SSB and configured via a PBCH configuration.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, identifying the search spacefurther includes removing time resources from the identified RMSI searchspace that overlap with the identified set of time resources, where theidentified search space includes remaining time resources of theidentified RMSI search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, removing the time resourcesfor the identified RMSI search space includes altering a slot-levelperiodicity of the identified RMSI search space, where the identifiedsearch space comprises same symbol index locations as the identifiedRMSI search space but with the altered slot-level periodicity of theidentified RMSI search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, identifying the search spacefurther includes identifying an RMSI search space with time resourcesnon-overlapping with the identified set of time resources, where theidentified search space includes the identified RMSI search space.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for transmitting, to the UE, anindication of a set of time resources for the search space. Someexamples of the method, apparatus, and non-transitory computer-readablemedium described herein may further include processes, features, means,or instructions for removing time resources of the identified set oftime resources from the indicated set of time resources for the searchspace, where the identified search space includes remaining timeresources of the indicated set of time resources for the search space.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein, the indication of the set oftime resources for the search space includes a time window for thesearch space. In some examples of the method, apparatus, andnon-transitory computer-readable medium described herein, a subset ofslots of the time window include the identified search space. In someexamples of the method, apparatus, and non-transitory computer-readablemedium described herein, the subset of slots includes each slot of thetime window.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for transmitting, to the UE, the SSB,where the first RACH message may be received in a RACH occasioncorresponding to the SSB.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate examples of wireless communications systemsthat support search space configurations for random access (RACH)messaging in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a signaling timeline that supportssearch space configurations for RACH messaging in accordance withaspects of the present disclosure.

FIG. 4 illustrates examples of potential multiplexing patterns thatsupport search space configurations for RACH messaging in accordancewith aspects of the present disclosure.

FIG. 5 illustrates an example of a process flow that supports searchspace configurations for RACH messaging in accordance with aspects ofthe present disclosure.

FIGS. 6 through 8 show block diagrams of a device that supports searchspace configurations for RACH messaging in accordance with aspects ofthe present disclosure.

FIG. 9 illustrates a block diagram of a system including a userequipment (UE) that supports search space configurations for RACHmessaging in accordance with aspects of the present disclosure.

FIGS. 10 through 12 show block diagrams of a device that supports searchspace configurations for RACH messaging in accordance with aspects ofthe present disclosure.

FIG. 13 illustrates a block diagram of a system including a base stationthat supports search space configurations for RACH messaging inaccordance with aspects of the present disclosure.

FIGS. 14 through 16 show flowcharts illustrating methods for searchspace configurations for RACH messaging in accordance with aspects ofthe present disclosure.

DETAILED DESCRIPTION

In some wireless communications systems (e.g., new radio (NR) systems),a user equipment (UE) may perform a random access (RACH) procedure witha base station to gain access to the wireless network. This RACHprocedure may include the communication of a number of messages betweenthe UE and base station, including RACH message 1 (Msg1), message 2(Msg2), message 3 (Msg3), and message 4 (Msg4) transmissions. The UE maytransmit the RACH Msg1 (e.g., a RACH preamble transmission) to the basestation to initiate the RACH procedure. In some cases, the UE mayreceive a set of synchronization signal blocks (SSBs) from the basestation, and may select one of the SSBs to utilize for the RACH Msg1transmission. The base station may respond to the RACH Msg1 with a RACHMsg2 (e.g., a random access response (RAR) message within a RAR window).The UE may then transmit a RACH Msg3 (e.g., a radio resource control(RRC) connection request) and receive a RACH Msg4 (e.g., a medium accesscontrol (MAC) control element (CE) for contention resolution) from thebase station in response. The scheduling of each of these messages maybe based on physical downlink control channel (PDCCH) signaling from thebase station to the UE. In order to receive the PDCCH signaling (e.g., aPDCCH grant) while supporting efficient retransmission capabilities, theUE may identify RACH message 2, 3, or 4 (Msg 2/3/4) search spaces tomonitor for the corresponding PDCCH transmissions.

For example, the UE may identify a set of SSB transmissions performed bythe base station. In some cases, the UE may determine this set of SSBsbased on remaining minimum system information (RMSI) signaling from thebase station. The UE may identify SSBs of the set of SSBs that are notquasi-co-located (QCL) with the selected SSB for the RACH procedure andmay determine time resources used by the base station for these non-QCLSSB transmissions. The UE may identify a search space (e.g., a defaultor configured Msg 2/3/4 search space) that does not overlap with thetime resources for these non-QCL SSBs. This may allow the UE to switchreceive beams in order to monitor for PDCCH transmissions in the Msg2/3/4 search space and monitor for the non-QCL SSBs.

In a first example, the UE may determine an RMSI search space configuredvia a physical broadcast channel (PBCH) transmission and may modify theRMSI search space by removing any resources that conflict in time withthe time resources for the non-QCL SSBs. The UE may identify a Msg 2/3/4search space contained within a response window (e.g., a RAR window)using the monitoring occasions of the modified RMSI search space. In asecond example, the UE may use a valid RMSI search space that does notoverlap with the time resources for the non-QCL SSBs as the Msg 2/3/4search space, where the valid RMSI search space may not be signaled inthe PBCH. In a third example, the UE may receive a Msg 2/3/4 searchspace configuration from the base station. This configuration mayinclude a time range and symbol allocation across the time range—asopposed to specific symbol allocations for each slot—for reducedconfiguration signaling overhead. The identified Msg 2/3/4 search spacemay be based on the indicated time range and symbol allocation, but mayremove resources from the configuration that overlap with the timeresources for the non-QCL SSBs. In any of the examples described herein,the UE may monitor the identified search space to receive PDCCHtransmissions while maintaining the ability to receive non-QCL SSBs fromthe base station. Receiving these non-QCL SSBs may reduce latency andimprove reliability of RACH message retransmissions by the UE during theRACH procedure.

Aspects of the disclosure are initially described in the context ofwireless communications systems. Additional aspects of the disclosureare described with respect to signaling timelines, multiplexingpatterns, and process flows. Aspects of the disclosure are furtherillustrated by and described with reference to apparatus diagrams,system diagrams, and flowcharts that relate to search spaceconfigurations for RACH messaging.

FIG. 1 illustrates an example of a wireless communications system 100that supports search space configurations for RACH messaging inaccordance with aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A)network, an LTE-A Pro network, or an NR network. In some cases, wirelesscommunications system 100 may support enhanced broadband communications,ultra-reliable (e.g., mission critical) communications, low latencycommunications, or communications with low-cost and low-complexitydevices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation Node B orgiga-nodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up only a portion of the geographic coverage area110, and each sector may be associated with a cell. For example, eachbase station 105 may provide communication coverage for a macro cell, asmall cell, a hot spot, or other types of cells, or various combinationsthereof. In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap, and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer. Insome examples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples,half-duplex communications may be performed at a reduced peak rate.Other power conservation techniques for UEs 115 include entering a powersaving “deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105, or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1 or otherinterface). Base stations 105 may communicate with one another overbackhaul links 134 (e.g., via an X2 or other interface) either directly(e.g., directly between base stations 105) or indirectly (e.g., via corenetwork 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 MHz to 300 GHz.Generally, the region from 300 MHz to 3 GHz is known as the ultra-highfrequency (UHF) region or decimeter band, since the wavelengths rangefrom approximately one decimeter to one meter in length. UHF waves maybe blocked or redirected by buildings and environmental features.However, the waves may penetrate structures sufficiently for a macrocell to provide service to UEs 115 located indoors. Transmission of UHFwaves may be associated with smaller antennas and shorter range (e.g.,less than 100 km) compared to transmission using the smaller frequenciesand longer waves of the high frequency (HF) or very high frequency (VHF)portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that can tolerate interference from otherusers.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band such as the 5 GHz ISM band. When operating inunlicensed radio frequency spectrum bands, wireless devices such as basestations 105 and UEs 115 may employ listen-before-talk (LBT) proceduresto ensure a frequency channel is clear before transmitting data. In somecases, operations in unlicensed bands may be based on a CA configurationin conjunction with CCs operating in a licensed band (e.g., LAA).Operations in unlicensed spectrum may include downlink transmissions,uplink transmissions, peer-to-peer transmissions, or a combination ofthese. Duplexing in unlicensed spectrum may be based on frequencydivision duplexing (FDD), time division duplexing (TDD), or acombination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving devices are equipped with one ormore antennas. MIMO communications may employ multipath signalpropagation to increase the spectral efficiency by transmitting orreceiving multiple signals via different spatial layers, which may bereferred to as spatial multiplexing. The multiple signals may, forexample, be transmitted by the transmitting device via differentantennas or different combinations of antennas. Likewise, the multiplesignals may be received by the receiving device via different antennasor different combinations of antennas. Each of the multiple signals maybe referred to as a separate spatial stream, and may carry bitsassociated with the same data stream (e.g., the same codeword) ordifferent data streams. Different spatial layers may be associated withdifferent antenna ports used for channel measurement and reporting. MIMOtechniques include single-user MIMO (SU-MIMO) where multiple spatiallayers are transmitted to the same receiving device, and multiple-userMIMO (MU-MIMO) where multiple spatial layers are transmitted to multipledevices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g., synchronizationsignals, reference signals, beam selection signals, or other controlsignals) may be transmitted by a base station 105 multiple times indifferent directions, which may include a signal being transmittedaccording to different beamforming weight sets associated with differentdirections of transmission. Transmissions in different beam directionsmay be used to identify (e.g., by the base station 105 or a receivingdevice, such as a UE 115) a beam direction for subsequent transmissionand/or reception by the base station 105. Some signals, such as datasignals associated with a particular receiving device, may betransmitted by a base station 105 in a single beam direction (e.g., adirection associated with the receiving device, such as a UE 115). Insome examples, the beam direction associated with transmissions along asingle beam direction may be determined based on a signal that wastransmitted in different beam directions. For example, a UE 115 mayreceive one or more of the signals transmitted by the base station 105in different directions, and the UE 115 may report to the base station105 an indication of the signal it received with a highest signalquality, or an otherwise acceptable signal quality. Although thesetechniques are described with reference to signals transmitted in one ormore directions by a base station 105, a UE 115 may employ similartechniques for transmitting signals multiple times in differentdirections (e.g., for identifying a beam direction for subsequenttransmission or reception by the UE 115), or transmitting a signal in asingle direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., a UE 115, which may be an example of a mmWreceiving device) may try multiple receive beams when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets applied to signals receivedat a set of antenna elements of an antenna array, or by processingreceived signals according to different receive beamforming weight setsapplied to signals received at a set of antenna elements of an antennaarray, any of which may be referred to as “listening” according todifferent receive beams or receive directions. In some examples areceiving device may use a single receive beam to receive along a singlebeam direction (e.g., when receiving a data signal). The single receivebeam may be aligned in a beam direction determined based on listeningaccording to different receive beam directions (e.g., a beam directiondetermined to have a highest signal strength, highest signal-to-noiseratio, or otherwise acceptable signal quality based on listeningaccording to multiple beam directions).

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays, which may support MIMOoperations, or transmit or receive beamforming. For example, one or morebase station antennas or antenna arrays may be co-located at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may have an antenna array witha number of rows and columns of antenna ports that the base station 105may use to support beamforming of communications with a UE 115.Likewise, a UE 115 may have one or more antenna arrays that may supportvarious MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-basednetwork that operate according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may insome cases perform packet segmentation and reassembly to communicateover logical channels. A MAC layer may perform priority handling andmultiplexing of logical channels into transport channels. The MAC layermay also use hybrid automatic repeat request (HARQ) to provideretransmission at the MAC layer to improve link efficiency. In thecontrol plane, the RRC protocol layer may provide establishment,configuration, and maintenance of an RRC connection between a UE 115 anda base station 105 or core network 130 supporting radio bearers for userplane data. At the Physical (PHY) layer, transport channels may bemapped to physical channels.

In some cases, UEs 115 and base stations 105 may support retransmissionsof data to increase the likelihood that data is received successfully.HARQ feedback is one technique of increasing the likelihood that data isreceived correctly over a communication link 125. HARQ may include acombination of error detection (e.g., using a cyclic redundancy check(CRC)), forward error correction (FEC), and retransmission (e.g.,automatic repeat request (ARQ)). HARQ may improve throughput at the MAClayer in poor radio conditions (e.g., signal-to-noise conditions). Insome cases, a wireless device may support same-slot HARQ feedback, wherethe device may provide HARQ feedback in a specific slot for datareceived in a previous symbol in the slot. In other cases, the devicemay provide HARQ feedback in a subsequent slot, or according to someother time interval.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period of T_(s)=1/30,720,000 seconds. Time intervals of a communications resource may beorganized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100, andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriers(CCs) using sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an evolved universalterrestrial radio access (E-UTRA) absolute radio frequency channelnumber (EARFCN)), and may be positioned according to a channel rasterfor discovery by UEs 115. Carriers may be downlink or uplink (e.g., inan FDD mode), or be configured to carry downlink and uplinkcommunications (e.g., in a TDD mode). In some examples, signal waveformstransmitted over a carrier may be made up of multiple sub-carriers(e.g., using multi-carrier modulation (MCM) techniques such asorthogonal frequency division multiplexing (OFDM) or discrete Fouriertransform-spread-OFDM (DFT-s-OFDM)).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR,etc.). For example, communications over a carrier may be organizedaccording to TTIs or slots, each of which may include user data as wellas control information or signaling to support decoding the user data. Acarrier may also include dedicated acquisition signaling (e.g.,synchronization signals or system information, etc.) and controlsignaling that coordinates operation for the carrier. In some examples(e.g., in a carrier aggregation (CA) configuration), a carrier may alsohave acquisition signaling or control signaling that coordinatesoperations for other carriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or resource blocks (RBs)) within a carrier (e.g., “in-band”deployment of a narrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations105 or UEs 115) may have a hardware configuration that supportscommunications over a particular carrier bandwidth, or may beconfigurable to support communications over one of a set of carrierbandwidths. In some examples, the wireless communications system 100 mayinclude base stations 105 and/or UEs that can support simultaneouscommunications via carriers associated with more than one differentcarrier bandwidth.

Wireless communications system 100 may support communication with a UE115 on multiple cells or carriers, a feature which may be referred to asCA or multi-carrier operation. A UE 115 may be configured with multipledownlink CCs and one or more uplink CCs according to a carrieraggregation configuration. CA may be used with both FDD and TDD CCs.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider carrier or frequency channel bandwidth, shortersymbol duration, shorter TTI duration, or modified control channelconfiguration. In some cases, an eCC may be associated with a CAconfiguration or a dual connectivity configuration (e.g., when multipleserving cells have a suboptimal or non-ideal backhaul link). An eCC mayalso be configured for use in unlicensed spectrum or shared spectrum(e.g., where more than one operator is allowed to use the spectrum). AneCC characterized by wide carrier bandwidth may include one or moresegments that may be utilized by UEs 115 that are not capable ofmonitoring the whole carrier bandwidth or are otherwise configured touse a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration may beassociated with increased spacing between adjacent subcarriers. Adevice, such as a UE 115 or base station 105, utilizing eCCs maytransmit wideband signals (e.g., according to frequency channel orcarrier bandwidths of 20, 40, 60, 80 MHz, etc.) at reduced symboldurations (e.g., 16.67 microseconds). A TTI in eCC may consist of one ormultiple symbol periods. In some cases, the TTI duration (that is, thenumber of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize anycombination of licensed, shared, and unlicensed spectrum bands, amongothers. The flexibility of eCC symbol duration and subcarrier spacingmay allow for the use of eCC across multiple spectrums. In someexamples, NR shared spectrum may increase spectrum utilization andspectral efficiency, specifically through dynamic vertical (e.g., acrossfrequency) and horizontal (e.g., across time) sharing of resources.

In some wireless communications systems, a UE 115 may perform a RACHprocedure with a base station 105 to gain access to the wirelessnetwork. This RACH procedure may include the communication of a numberof messages between the UE 115 and base station 105, including RACHMsg1, Msg2, Msg3, and Msg4 transmissions. The UE 115 may transmit theRACH Msg1 (e.g., a RACH preamble transmission) to the base station 105to initiate the RACH procedure. In some cases, the UE 115 may receive aset of SSBs from the base station 105, and may select one of the SSBs toutilize for the RACH Msg1 transmission. The base station 105 may respondto the RACH Msg1 with a RACH Msg2 (e.g., a RAR message within a RARwindow). The UE 115 may then transmit a RACH Msg3 (e.g., an RRCconnection request), and receive a RACH Msg4 (e.g., a MAC CE forcontention resolution) from the base station 105 in response. Thescheduling of each of these messages may be based on PDCCH signalingfrom the base station 105 to the UE 115. In order to receive the PDCCHsignaling while supporting efficient retransmission capabilities, the UE115 may identify RACH Msg 2/3/4 search spaces to monitor for thecorresponding PDCCH transmissions.

For example, the UE 115 may identify a set of SSB transmissionsperformed by the base station 105. In some cases, the UE 115 maydetermine this set of SSBs based on RMSI signaling from the base station105. The UE 115 may identify SSBs of the set of SSBs that are not QCLwith the selected SSB for the RACH procedure, and may determine timeresources used by the base station 105 for these non-QCL SSBtransmissions. The UE 115 may identify a search space (e.g., a defaultor configured Msg 2/3/4 search space) that does not overlap with thetime resources for these non-QCL SSBs.

In a first example, the UE 115 may determine an RMSI search spaceconfigured via a PBCH transmission, and may modify the RMSI search spaceby removing any resources that conflict in time with the time resourcesfor the non-QCL SSBs. The UE 115 may identify a Msg 2/3/4 search spacecontained within a response window (e.g., a RAR window) using themonitoring occasions of the modified RMSI search space. In a secondexample, the UE 115 may use a valid RMSI search space that does notoverlap with the time resources for the non-QCL SSBs as the Msg 2/3/4search space, where the valid RMSI search space may not be signaled inthe PBCH. In a third example, the UE 115 may receive a Msg 2/3/4 searchspace configuration from the base station 105. This configuration mayinclude a time range and symbol allocation across the time range—asopposed to specific symbol allocations for each slot—for reducedconfiguration signaling overhead. The identified Msg 2/3/4 search spacemay be based on the indicated time range and symbol allocation, but mayremove resources from the configuration that overlap with the timeresources for the non-QCL SSBs. In any of the examples described herein,the UE 115 may monitor the identified search space to receive PDCCHtransmissions while maintaining the ability to receive non-QCL SSBs fromthe base station 105. Receiving these non-QCL SSBs may reduce latencyand improve reliability of RACH message retransmissions by the UE 115during the RACH procedure.

FIG. 2 illustrates an example of a wireless communications system 200that supports search space configurations for RACH message responses inaccordance with aspects of the present disclosure. The wirelesscommunications system 200 may include base station 105-a and UE 115-a,which may be examples of a base station 105 and a UE 115 as describedwith reference to FIG. 1. Base station 105-a may provide networkcoverage for geographic coverage area 110-a. As illustrated, UE 115-amay perform a RACH procedure to gain access to the network. The RACHprocedure may involve UE 115-a receiving downlink RACH messaging in adefault or configured search space.

For example, base station 105-a may periodically or aperiodicallytransmit a set of SSBs 210 on different transmit beams 205 (e.g., in abeam-sweep procedure). These different SSBs 210 may be transmitted byQCL or non-QCL antennas at the base station 105-a. For UE 115-a toaccess the network, UE 115-a may monitor for SSBs 210 transmitted bybase station 105-a. In some cases, UE 115-a may detect and decodemultiple SSBs 210 from base station 105-a on different receive beams215. For example, base station 105-a may transmit SSB 210-a on transmitbeam 205-a and SSB 210-b on transmit beam 205-b, and UE 115-a mayreceive the SSBs 210 on receive beam 215-a and receive beam 215-b,respectively. UE 115-a may select one of these SSBs 210 (e.g., based ona receive power or channel quality associated with the SSB 210) and mayperform a RACH procedure based on information in the selected SSB 210.For example, UE 115-a may select SSB 210-a and may transmit a RACHmessage 220 based on information or parameters in SSB 210-a. This RACHmessage 220 may be an example of a RACH Msg1 or a RACH Msg3.

UE 115-a may monitor for a PDCCH signal. This signal may be PDCCHcomponents of a RACH Msg2, a RACH Msg3, or a RACH Msg4 (RACH Msg 2/3/4),such as a PDCCH grant. For example, the PDCCH signal may be a responseto the RACH message 220. In order to handle the RACH Msg 2/3/4, UE 115-amay monitor a search space for scheduling assignments or schedulinggrants corresponding to the RACH Msg 2/3/4. The search space may includea set of carrier channels formed by control channel elements (CCEs) at aspecific aggregation level. In some cases, UE 115-a may monitor multiplesearch spaces on same or different aggregation levels. UE 115-a mayattempt to decode (e.g., blind decode) any PDCCHs formed by the CCEswithin a search space for the UE 115-a. If a decoded PDCCH passes aparity check (e.g., a CRC), the UE 115-a may process the contents of thePDCCH. Processing this information may allow UE 115-a to correctlytransmit or receive certain RACH messages, such as RACH Messages 2, 3,or 4.

In some cases, UE 115-a may receive (e.g., via a PBCH transmission orSSB 210) a configuration of the search space. This configuration mayspecify symbol indices, slots, etc. for the search space, may specify atime range for the search space, or may specify a specific search space(e.g., with a random access search space higher layer parameter for aType1-PDCCH common search space). In other cases, UE 115-a may notreceive a configuration for the search space. In these cases, UE 115-amay identify a default search space to utilize in order to receive thePDCCH information. In some cases, this default search space may be basedon an RMSI search space (e.g., a Type0-PDCCH common search space). Forexample, the default search space may share an association betweenmonitoring occasions and SSBs 210 or PBCH transmissions with the RMSIsearch space. This default Msg 2/3/4 search space may be based on aresponse window (e.g., a RAR window) for the RACH message 220.

However, simply using the configured RMSI search space for the defaultMsg 2/3/4 search space may result in timing issues. For example, UE115-a may utilize a specific RMSI periodicity (e.g., 20 ms, if thecontrol resource set (CORESET) for the RMSI search space is TDM with theSSBs 210). However, UE 115-a may implement a RAR window of a differentlength or maximum length (e.g., 10 ms), which may be shorter than theRMSI periodicity. In certain cases, the RMSI search space may not belocated within the RAR window (e.g., based on the longer repetitionbetween repeat RMSI search spaces than the window). Accordingly, UE115-a may determine to retransmit the RACH message 220 based on thecompletion of the RAR window before monitoring for the response based onthe RMSI search space (e.g., the RAR search space may not be presentwithin the RAR window if the RAR search space directly corresponds tothe RMSI search space). Additionally, in some cases, UE 115-a may not beable to track SSBs 210 transmitted by base station 105-a in symbols usedby UE 115-a for monitoring the search space for PDCCH transmissions.

To better handle search space timing, the search space may be based onactually transmitted SSBs 210. For example, base stations 105 maysupport a number of SSBs 210 (e.g., sixty-four total SSBs 210). Each SSB210 of this group of SSBs 210 may or may not be QCL, and UE 115-a maytreat the SSBs 210 as if the SSBs 210 are non-QCL (e.g., whether or notthis assumption is technically correct). Each SSB 210 of this group ofSSBs 210 may correspond to a specific transmission direction. In somecases, base station 105-a may use a subset of this group of SSBs 210 andmay not use the other SSBs 210 based on a configuration or deployment ofbase station 105-a. Base station 105-a may indicate the SSBs 210 thatbase station 105-a actually transmits in the RMSI (e.g., using SSBindices, where each SSB index corresponds to an actually transmitted SSB210 and a transmission time for the SSB 210). UE 115-a may identify aset of time resources used for actual SSB 210 transmissions by basestation 105-a that are not QCL with the selected SSB 210. The searchspace (e.g., configured or default) for UE 115-a may avoid overlappingthis identified set of time resources.

In a first example, resources may be removed from a search space toresult in the Msg 2/3/4 search space. For example, for a configuredsearch space, UE 115-a may remove any resources from the configuredsearch space overlapping in time with the identified set of timeresources (e.g., the time resources used for actual SSB 210transmissions that are non-QCL with a selected SSB 210 transmission).For a default search space, UE 115-a may identify an RMSI search space(e.g., indicated in an SSB 210 or PBCH transmission). UE 115-a may usethe symbol locations of the RMSI search space for the Msg 2/3/4 searchspace, but may remove any symbol locations overlapping with theidentified set of time resources. In some cases, the Msg 2/3/4 may usethe same symbol locations as the RMSI search space, but may use adifferent slot-level periodicity in order to avoid the identified set oftime resources. For example, if there are twenty slots in a RAR window,and four of these slots have SSB symbol locations that overlap withsymbol locations of the search space, the Msg 2/3/4 search space may bemodified to remove these four slots and just span the other sixteenslots. In this way, the modified RMSI search space used for the Msg2/3/4 search space may avoid timing conflicts with non-QCL SSBs 210. Insome cases, this default search space may span the duration of a RARwindow, starting from the end of the RACH message 220 transmission.

In a second example, a valid RMSI search space not overlapping in timewith the identified set of time resources may be used for the Msg 2/3/4search space. In some cases, UE 115-a may determine an RMSI search spaceindicated in an SSB 210 or PBCH transmission and may identify that theRMSI search space overlaps in timing resources with the identified setof time resources. UE 115-a may select a different RMSI search spacethan the one indicated based on this timing resource conflict. In othercase, UE 115-a may automatically select a different RMSI search space nomatter the indicated search space in the SSB 210 or PBCH transmission.In some cases, UE 115-a may select an RMSI search space with a CORESETthat is TDM with the SSB 210 transmissions in order to avoid overlap intiming resources.

In any of the examples described herein, UE 115-a may identify the Msg2/3/4 search space based on the described techniques. Base station 105-amay utilize similar techniques to determine the CCE resources to use fora PDCCH transmission (e.g., for a RACH Msg 2/3/4). Base station 105-amay transmit the PDCCH transmission using the same transmit beam 205-aas the selected SSB 210-a, and UE 115-a may monitor the channel usingthe same receive beam 215-a that received SSB 210-a. UE 115-a maymonitor for the PDCCH transmission and the SSB 210-a using receive beam215-a during the time resources of the identified Msg 2/3/4 search spaceand may monitor for non-QCL SSBs 210 (e.g., SSB 210-b) using differentreceive beams (e.g., receive beam 215-b) during the identified set oftime resources. In this way, a UE 115 supporting a single receive beammay track non-QCL SSBs 210 during a RACH procedure in caseretransmissions of the RACH message 220 are needed. For examples, anyUEs 115 with a single antenna panel may implement this procedure toswitch between receive beams.

FIG. 3 illustrates an example of a signaling timeline 300 that supportssearch space configurations for RACH message responses in accordancewith aspects of the present disclosure. The signaling timeline 300 mayillustrate approximate timing of processes at a UE 115, as describedwith reference to FIGS. 1 and 2. This approximate timing may correspondto symbol indexes or locations within one or more TTIs, such as slots orsubframes. The timeline 300 may show reception of SSBs 310 at the UE115, RACH occasions 315 corresponding to the received SSBs 310, andmonitoring or reception of RACH Msg2 325 transmissions according to adefault search space. These signals or processes may be repeated in time305 based on a repetition process and a RAR window 320. While thesignaling timeline 300 is described with respect to RACH Msg2 325transmissions, the same or similar processes may be performed to receivePDCCH messages (e.g., grants) for any of the RACH messaging, includingRACH Msg3 and RACH Msg4 transmissions.

In some examples, a UE 115 may receive multiple SSBs 310 from a basestation 105. These SSBs 310 may be received at different times, and maybe received from different antennas or beams at the base station 105that are not QCL. Based on these SSBs 310 not being QCL, the UE 115 mayreceive a first SSB 310-a on a first receive beam, and may receive asecond SSB 310-b on a second receive beam. In some cases, the UE 115 mayreceive an SSB 310 on multiple receive beams, and may select one of thereceive beams to associate with the SSB 310 (e.g., based on a highestreference signal received power (RSRPs) of the receive beams).Additionally or alternatively, the UE 115 may receive other SSBs 310 onthe first receive beam, the second receive beam, additional receivebeams, or some combination thereof. The UE 115 may select one of theSSBs 310 for a RACH procedure. In some cases, the UE 115 may select theSSB 310 based on a signal quality, channel conditions, expectedreliability, or some similar parameter associated with the SSB 310. Asillustrated, the UE 115 may select SSB 310-b.

The UE 115 may perform a RACH message transmission in the RACH occasion315 corresponding to the selected SSB 310-b. In some cases, each SSB 310may correspond to a different RACH occasion 315 (e.g., SSB 310-acorresponding to RACH occasion 315-a and SSB 310-b corresponding to RACHoccasion 315-b). The base station 105 may transmit the SSBs 310 at thebeginning of a RACH configuration period, and the RACH occasions 315 maybe located at the end of the RACH configuration period. The UE 115 maytransmit a RACH message (e.g., a RACH Msg1) to the base station in RACHoccasion 315-b based on selecting SSB 310-b.

The UE 115 may monitor for a response from the base station 105 to thetransmitted RACH message. For example, the UE 115 may monitor for aresponse (e.g., a RACH Msg2 325 transmission) during a RAR window 320.If the UE 115 receives a response during the RAR window 320, the UE 115may proceed with a next step of the access procedure (e.g., transmittinganother type of RACH message, establishing a link, etc.). If the UE 115does not receive a response during the RAR window 320, the UE 115 mayretransmit the RACH message in another RACH occasion 315. If the RARwindow 320 include no backoff period or a minimal backoff period, the UE115 may retransmit the RACH message at any time following the RAR window320 (e.g., any time corresponding to a RACH occasion 315).

The UE 115 may transmit the RACH message in RACH occasion 315-baccording to the selected SSB 310-b. For example, the UE 115 may utilizea transmit beam based on the receive beam used to receive SSB 310-b, andmay monitor for responses using the same receive beam. This may be basedon demodulation reference signals (DMRSs) for the Msg2 grant being QCLwith selected SSB 310-b, where the UE 115 can receive QCL transmissionon a same receive beam, and may receive non-QCL transmissions ondifferent receive beams. The UE 115 may monitor for responses during aRAR window 320. In some cases, the RAR window 320 may begin after or attransmission of the RACH message (e.g., the utilized RACH occasion315-b) and may end based on a RAR timer or length. As illustrated, theRAR window 320 may overlap the SSB 310 locations.

If the UE 115 does not receive a search space configuration from thebase station 105, the UE 115 may identify a default search space toutilize to monitor for a response to the transmitted RACH message. Inother cases, the UE 115 may receive an indication of a search spaceconfiguration, where the search space configuration includes a starttime and an end time. Whether implementing a default or configuredsearch space for RACH response monitoring, the UE 115 may monitor onesearch space per TTI (e.g., slot). The starting symbol of the searchspace may remain the same for each of these slots. In some cases, the UE115 may monitor the search space in each slot within the RAR window 320(e.g., for a default search space where a start or end time is notindicated). For a default search space, the UE 115 may reuse symbollocations associated with an RMSI search space as the symbol locationsfor the default search space for the RACH response.

However, in some cases, utilizing a search space in each slot of the RARwindow 320 may result in overlapping the search space with timeresources used for SSB 310 transmissions. For example, the search spacemonitored by the UE 115 and an SSB 310 transmission by the base station105 may share a symbol location. To differentiate between a RACH Msg2325 transmission and an SSB 310 overlapping in time resources, the basestation 105 and UE 115 may perform FDM. If these transmissions are QCL(e.g., such as SSB 310-b and the RACH Msg2 325), this FDM procedure mayallow a same receive beam at the UE 115 to receive both of thetransmissions. However, if these transmissions are not QCL (e.g., suchas SSB 310-a and the RACH Msg2 325), the UE 115 may not receive thetransmissions on a same receive beam using the FDM procedure.Accordingly (e.g., if the UE 115 operates using one receive beam at atime), the UE 115 may not be able to track SSB 310-a while monitoringfor the response message on the receive beam corresponding to SSB 310-b.

In some cases, the UE 115 may not successfully receive and decode a RACHMsg2 325 transmission during the RAR window 320. In these cases, thecompletion of the RAR window 320 may trigger the UE 115 to retransmitthe RACH message and again monitor for a response. If the UE 115 cannottrack SSB 310-a during the RAR window 320 (e.g., due to overlapping timeresources), the UE 115 may not utilize the RACH occasion 315-acorresponding to SSB 310-a that follows the RAR window 320. This mayincrease latency and reduce reliability of the RACH messagetransmissions. For example, assuming no backoff period—or aninsignificant backoff period—the UE 115 may retransmit the RACH messagein RACH occasion 315-a following the RAR window 320 if SSB 310-a isreceived, allowing the UE 115 to perform the retransmission faster thanif the UE 115 waits to retransmit the RACH message in RACH occasion315-b. However, if the UE 115 does not receive SSB 310-a during the RARwindow 320 (e.g., due to monitoring a search space using a receive beamassociated with SSB 310-b, not SSB 310-a), the UE 115 cannot utilize thecorresponding RACH occasion 315-a for RACH retransmission, and waits fora later RACH occasion 315 (e.g., for which the UE 115 received acorresponding SSB 310) for retransmission. Additionally, not receiving aRACH Msg2 325 during the RAR window 320 may be due to problems with thechannel (e.g., existence of interference, low signal-to-noise ratio(SNR), etc.). Repeating the transmission using SSB 310-b andcorresponding RACH occasion 315-b may have a greater probability offailing than using a different SSB 310 and RACH occasion 315, as thesame channel issues may persist across one or more retransmissions. Byswitching to a different SSB 310—and, correspondingly, a different RACHoccasion 315—the UE 115 may improve the probability of receiving a RACHMsg2 325 transmission in response to the RACH message (e.g., due todifferent channel conditions).

The issues with tracking an SSB 310 (e.g., SSB 310-a) associated with adifferent receive beam than the RACH Msg2 325 monitoring may persistacross RAR windows 320. For example, if the search space of RACH Msg2/3/4 starts at the same symbol in each slot, and the SSB 310 is not QCLwith the DMRS of Msg 2/3/4 and is transmitted at a same symbol in one ormore slots, these time resources may overlap in each RAR window 320.Accordingly, the UE 115 may not be able to track SSBs 310 not QCL withthe initially selected SSB 310-b during the entire retransmissionprocedure.

To handle this issue, the search spaces of Msg 2/3/4 may be defined tonot overlap with SSBs that are not QCL with DMRS of the Msg 2/3/4. Forexample, the UE 115 may identify the SSBs 310 actually transmitted bythe base station 105, and may determine time resources for these SSBs310. Once the UE 115 selects an SSB 310 for a RACH transmission, the UE115 may identify time resources used for transmissions of non-QCL SSBs310. For example, if the UE 115 selects SSB 310-b, then the UE 115 mayidentify the time resources for transmission of non-QCL SSB 310-a. Whenthe UE 115 determines the search space (e.g., a default or configuredsearch space) for monitoring for responses, the UE 115 may avoidoverlapping the search space time resources with the identified non-QCLSSB 310 time resources. In one case, this may involve identifying asearch space, and modifying the search space to not overlap in thesetime resources (e.g., based on a priority level associated with thesearch space, the time resources, or both). For example, the UE 115 mayalter the slot-periodicity of a search space, or may modify the searchspace at the symbol-level. In a second case, this may involve selectinga search space that does not overlap with the time resources for theidentified non-QCL SSB 310.

In any of the cases described herein, by not overlapping the timeresources of the search space and the non-QCL SSBs 310, the UE 115 maymonitor for both the SSBs 310 and the RACH Msg2 325 transmission. Forexample, the UE 115 may monitor for the RACH Msg2 325 transmission andSSB 310-b using one receive beam at one time, and may switch to monitorfor SSB 310-a using a different receive beam at a different time. Thismay allow the UE 115 to perform retransmissions with reduced latency andimproved reliability, and may allow the UE 115 to efficiently utilizethe RAR window 320.

FIG. 4 illustrates examples of potential multiplexing patterns 400 thatsupport search space configurations for RACH messaging in accordancewith aspects of the present disclosure. The potential multiplexingpatterns 400 may be used by a base station 105 for transmission and by aUE 115 for reception, as described herein with reference to FIGS. 1through 3. Each pattern 405 illustrates approximations of time 410 andfrequency 415 resources used for an SS/PBCH block 420 (e.g., or anysimilar synchronization signals), a CORESET 425 (e.g., an RMSI PDCCHtransmission), and a physical downlink shared channel (PDSCH) 430 (e.g.,an RMSI PDSCH transmission). These are just a few examples of potentialmultiplexing patterns 400, and other patterns 405 may be implemented.

Pattern 405-a illustrates a TDM example. The SS/PBCH block 420, CORESET425, and PDSCH 430 share frequency resources 415-a (e.g., at least asubset of frequency resources), but utilize different time resources410-a. In some cases, a UE 115 may select a pattern such as this for anRMSI search space CORESET, so that the SS/PBCH block 420 and the CORESET425 do not overlap in time resources 410-a. In these cases, the UE 115may not remove time resources from the selected RMSI search space.

Pattern 405-b illustrates a combination of a TDM example and an FDMexample. The SS/PBCH block 420 and PDSCH 430 may share time resources410-b (e.g., at least a subset of time resources), but utilize differentfrequency resources 415-b. Meanwhile, the CORESET 425 may sharefrequency resources 415-b but not time resources 410-b with the PDSCH430, and may not share either time or frequency resources with theSS/PBCH block 420. In this way, as with pattern 405-a, a UE 115 mayselect an RMSI search space with a CORESET 425 defined in this way toavoid overlapping the CORESET 425 and the SS/PBCH block 420 in timeresources 410-b.

Pattern 405-c illustrates a combination of a TDM example and an FDMexample. The CORESET 425 and PDSCH 430 may share frequency resources415-c, but not time resources 410-c. Meanwhile, the SS/PBCH block 420may share time resources 410-c but not frequency resources 415-c withthe PDSCH 430 and the CORESET 425. In patterns 405 such as this, if a UE115 selects an RMSI search space with a CORESET 425 defined in this way,the UE 115 may identify time resources 410-c of non-QCL SSBs/PBCH of theSS/PBCH block 420, and may remove these time resources 410-c from theCORESET 425 (e.g., to avoid overlapping these time resources 410-c).

If a UE 115 determines that a CORESET for an RMSI search space (e.g., aType0-PDCCH common search space) is present, the UE 115 may determine anumber of consecutive RBs and a number of consecutive symbols for theCORESET of the RMSI search space from a first set of bits (e.g., thefour most significant bits of the RMSI PDCCH configuration), and maydetermine PDCCH monitoring occasions from a second set of bits (e.g.,the four least significant bits of RMSI PDCCH configuration) included ina master information block (MIB). Tables 1 through 5, presented below,illustrate possible techniques for determining monitoring occasionsbased on specific parameters.

TABLE 1 Parameters for PDCCH monitoring occasions for Type0-PDCCH commonsearch space - SS/PBCH block and CORESET multiplexing pattern 405-a andFR1 Number of search Index O space sets per slot M First symbol index 00 1 1 0 1 0 2 1/2 {0, if i is even}, {N_(symb) ^(CORESET), if i is odd}2 2 1 1 0 3 2 2 1/2 {0, if i is even}, {N_(symb) ^(CORESET), if i isodd} 4 5 1 1 0 5 5 2 1/2 {0, if, is even}, {N_(symb) ^(CORESET), if i isodd} 6 7 1 1 0 7 7 2 1/2 {0, if i is even}, {N_(symb) ^(CORESET), if iis odd} 8 0 1 2 0 9 5 1 2 0 10 0 1 1 1 11 0 1 1 2 12 2 1 1 1 13 2 1 1 214 5 1 1 1 15 5 1 1 2

TABLE 2 Parameters for PDCCH monitoring occasions for Type0-PDCCH commonsearch space - SS/PBCH block and CORESET multiplexing pattern 405-a andFR2 Number of search Index O space sets per slot M First symbol index 00 1 1 0 1 0 2 1/2 {0, if i is even}, {7, if i is odd} 2 2.5 1 1 0 3 2.52 1/2 {0, if i is even}, {7, if i is odd} 4 5 1 1 0 5 5 2 1/2 {0, if iis even}, {7, if i is odd} 6 0 2 1/2 {0, if i is even}, {N_(symb)^(CORESET), if i is odd} 7 2.5 2 1/2 {0, if i is even}, {N_(symb)^(CORESET), if i is odd} 8 5 2 1/2 {0, if i is even}, {N_(symb)^(CORESET), if i is odd} 9 7.5 1 1 0 10 7.5 2 1/2 {0, if i is even}, {7,if i is odd} 11 7.5 2 1/2 {0, if i is even}, {N_(symb) ^(CORESET), if iis odd} 12 0 1 2 0 13 5 1 2 0 14 Reserved 15 Reserved

TABLE 3 PDCCH monitoring occasions for Type0-PDCCH common search space -SS/PBCH block and CORESET multiplexing pattern 405-b and {SS/PBCH block,PDCCH} subcarrier spacing {120, 60} kHz PDCCH monitoring occasions Firstsymbol index Index (SFN and slot number) (k = 0, 1, . . . 15) 0 SFN_(C)= SFN_(SSB,j) 0, 1, 6, 7 for n_(C) = n_(SSB,j) i = 4k, i = 4k + 1, i =4k + 2, i = 4k + 3 1 Reserved 2 Reserved 3 Reserved 4 Reserved 5Reserved 6 Reserved 7 Reserved 8 Reserved 9 Reserved 10 Reserved 11Reserved 12 Reserved 13 Reserved 14 Reserved 15 Reserved

TABLE 4 PDCCH monitoring occasions for Type0-PDCCH common search space -SS/PBCH block and CORESET multiplexing pattern 405-b and {SS/PBCH block,PDCCH} subcarrier spacing {240, 120} kHz PDCCH monitoring occasions (SFNand slot First symbol index Index number) (k = 0, 1, . . . , 7) 0SFN_(C) = SFN_(SSB,i) 0, 1, 2, 3, 0, 1 in i = 8k, n_(C) = n_(SSB,i) orn_(C) = n_(SSB,i) − 1 i = 8k + 1, i = 8k + 2, i = 8k + 3, i = 8k + 6, i= 8k + 7 (n_(C) = n_(SSB,i)) 12, 13 in i = 8k + 4, i = 8k + 5 (n_(C) =n_(SSB,i) − 1) 1 Reserved 2 Reserved 3 Reserved 4 Reserved 5 Reserved 6Reserved 7 Reserved 8 Reserved 9 Reserved 10 Reserved 11 Reserved 12Reserved 13 Reserved 14 Reserved 15 Reserved

TABLE 5 PDCCH monitoring occasions for Type0-PDCCH common search space -SS/PBCH block and CORESET multiplexing pattern 405-c and {SS/PBCH block,PDCCH} subcarrier spacing {120, 120} kHz PDCCH monitoring occasionsFirst symbol index Index (SFN and slot number) (k = 0, 1, . . . 15) 0SFN_(C) = SFN_(SSB,i) 4, 8, 2, 6 in n_(C) = n_(SSB,i) i = 4k, i = 4k +1, i = 4k + 2, i = 4k + 3 1 Reserved 2 Reserved 3 Reserved 4 Reserved 5Reserved 6 Reserved 7 Reserved 8 Reserved 9 Reserved 10 Reserved 11Reserved 12 Reserved 13 Reserved 14 Reserved 15 Reserved

In the above tables, SFN_(C) and n_(C) are the SFN and slot index of theCORESET based on subcarrier spacing of the CORESET, SFN_(SSB,i) andn_(SSB,i) are the SFN and slot index based on subcarrier spacing of theCORESET when the SS/PBCH block 420 with index i overlaps in time withsystem frame SFN_(SSB,i) and slot n_(SSB,i).

In some cases, an offset may be defined with respect to the subcarrierspacing of the CORESET from the smallest RB index of the CORESET for anRMSI search space to the smallest RB index of the common RB overlappingwith the first RB of the SS/PBCH block 420.

For pattern 405-a, a UE 115 may monitor PDCCH in the RMSI search spaceCORESET 425 over two consecutive slots starting from a slot, n₀, wheren₀=(0·2^(μ)+└i·M┘)mod N_(slot) ^(frame,μ) located in a frame withSFN_(C) satisfying SFN_(C) mod 2=0 if

${\left\lbrack \frac{{O \cdot 2^{\mu}} + \left\lfloor {i \cdot M} \right\rfloor}{N_{slot}^{{frame},\mu}} \right\rbrack {mod}\mspace{14mu} 2} = 0$

or in a frame with SFN satisfying SFN_(C) mod 2=1 if

${\left\lbrack \frac{{O \cdot 2^{\mu}} + \left\lfloor {i \cdot M} \right\rfloor}{N_{slot}^{{frame},\mu}} \right\rbrack {mod}\mspace{14mu} 2} = 1.$

Values for M and O may be found in Tables 1 and 2, and μ∈{0,1,2,3} basedon the subcarrier spacing for PDCCH receptions in the CORESET. The indexfor the first symbol of the CORESET in slot n_(C) may be the firstsymbol index provided Tables 1 and 2.

For patterns 405-b and 405-c, a UE 115 may monitor PDCCH in the RMSIsearch space over one slot with RMSI search space periodicity equal tothe periodicity of the corresponding SS/PBCH block 420. For an SS/PBCHblock 420 with index i, the UE 115 may determine the slot index n_(C)and SFN_(C) based on the parameters provided in tables 3 through 5.

If a UE 115 detects a first SS/PBCH block 420 and determines that aCORESET 425 for an RMSI search space is not present, and for certainfrequency ranges (FRs) (e.g., 24≤k_(SSB)≤29 for FR1 or for 12≤k_(SSB)≤13for FR2), the UE 115 may determine the global synchronization channelnumber (GSCN) of a second SS/PBCH block 420 having a CORESET for anassociated RMSI search space as N_(GSCN) ^(Reference)+N_(GSCN)^(Offset), where N_(GSCN) ^(Reference) is the GSCN of the first SS/PBCHblock 420 and N_(GSCN) ^(Offset) is the GSCN offset is provided byTables 6 and 7 presented below, where Table 6 corresponds to FR1 (e.g.,450 MHz to 6000 MHz) and Table 7 corresponds to FR2 (e.g., 24250 MHz to52600 MHz).

If a UE 115 detects an SS/PBCH block 420 and determines that a CORESETfor the RMSI search space is not present, for certain FRs (e.g.,k_(SSB)=31 for FR1 or k_(SSB)=15 for FR2), the UE 115 may determine thatthere is no SS/PBCH block having an associated RMSI search space withina GSCN range [N_(GSCN) ^(Reference)−N_(GSCN) ^(Start), N_(GSCN)^(Reference)+N_(GSCN) ^(End)], where N_(GSCN) ^(Start) and N_(GSCN)^(End) are determined based on a first set of bits (e.g., four mostsignificant bits) and a second set of bits (e.g., four least significantbits) of an RMSI PDCCH configuration, respectively.

TABLE 6 Mapping between the combination of k_(SSB) and RMSI PDCCHConfiguration to N_(GSCN) ^(Offset) for FR1 k_(SSB) RMSI-PDCCH-ConfigN_(GSCN) ^(Offset) 24 0, 1, . . . , 255 1, 2, . . . , 256 25 0, 1, . . ., 255 257, 258, . . . , 512 26 0, 1, . . . , 255 513, 514, . . . , 76827 0, 1, . . . , 255 −1, −2 . . . , −256 28 0, 1, . . . , 255 −257, −258. . . , −512 29 0, 1, . . . , 255 −513, −514 . . . , −768 30 0, 1, . . ., 255 Reserved, Reserved, . . . , Reserved

TABLE 7 Mapping between the combination of k_(SSB) and RMSI PDCCHConfiguration to N_(GSCN) ^(Offset) for FR2 k_(SSB) RMSI-PDCCH-ConfigN_(GSCN) ^(Offset) 12 0, 1, . . . , 255 1, 2, . . . , 256 13 0, 1, . . ., 255 −1, −2, . . . , −256 14 0, 1, . . . , 255 Reserved, Reserved, . .. , Reserved

FIG. 5 illustrates an example of a process flow 500 that supports searchspace configurations for RACH messaging in accordance with aspects ofthe present disclosure. Process flow 500 may include base station 105-band UE 115-b, which may be examples of the devices described withrespect to FIGS. 1 and 2. UE 115-b may determine a search space forreceiving downlink RACH messaging (e.g., PDCCH signals) based on SSBtransmission timing. In some implementations, the processes describedherein may be performed in a different order, or may include one or moreadditional or alternative processes performed by the wireless devices.

At 505, base station 105-b may transmit a set of SSBs. UE 115-b mayreceive the set of SSBs, and may select one SSB of the set of SSBs. Insome cases, UE 115-b may receive different SSBs on different receivebeams based on whether or not the SSB transmissions are QCL. Forexample, UE 115-b may receive the SSB on a first receive beam, and mayreceive one or more other SSBs of the set of SSBs on receive beamsdifferent from the first receive beam. At 510, UE 115-b may transmit, tobase station 105-b, a first RACH message based on the selected SSB. Forexample, UE 115-b may transmit the first RACH message in a RACH occasioncorresponding to the selected SSB.

At 515, UE 115-b and base station 105-b may identify a set of timeresources used by base station 105-b for transmission of the one or moreother SSBs. These other SSBs may be received by UE 115-b on receivebeams that are different from the first receive beams. The identifiedset of time resources may correspond to the time resources used for SSBsthat cannot be received by UE 115-b on a same beam as the selected SSB.

At 520, UE 115-b and base station 105-b may identify a search space forreceiving a PDCCH message based on the first RACH message, where theidentified search space includes time resources that are different fromthe identified set of time resources. For example, the search space maynot include any time resources overlapping the identified set of timeresources. In some cases, the search space may be an example of amodified RMSI search space indicated via a PBCH configuration, where theRMSI search space is modified to remove resource overlapping in timewith the identified set of time resources. In other cases, the searchspace may be an example of a valid RMSI search space (e.g., notindicated via a PBCH configuration) that does not overlap with theidentified set of time resources. For example, the search space may usea pattern where the PDCCH CORESET is not TDM with synchronizationsignals. In yet other cases, UE 115-b may receive a configuration forthe search space, and may remove time resources from the configuredsearch space that overlap with the identified set of time resources. Inany of these cases, the resulting search space used to monitor fortransmissions may not overlap in time with non-QCL SSB transmissions.

At 525, base station 105-b may map the PDCCH message to CCEs within theidentified search space. This PDCCH message may be an example of a PDCCHgrant for a RACH Msg 2/3/4. At 530, UE 115-b may monitor the searchspace for the PDCCH message transmission. UE 115-b may monitor for thetransmission using the first receive beam (e.g., the receive beam usedto receive the selected SSB).

At 535, base station 105-b may transmit the PDCCH message to UE 115-baccording to the mapping. In some cases, base station 105-b may transmitthe set of SSBs again at 540. UE 115-b may receive the non-QCL SSBsbased on switching receive beams. For example, UE 115-b may receivetransmissions using the first receive beam during time resources of thesearch space, and may receive transmissions using different receivebeams during the identified set of time resources for the non-QCL SSBs.If UE 115-b receives the PDCCH message (e.g., in response to the firstRACH message, during a reception window), UE 115-b may perform furtherRACH procedures. If UE 115-b does not receive the PDCCH message, UE115-b may perform a retransmission process (e.g., using the same SSB, orusing an additional received SSB, such as one of the non-QCL SSBs).

FIG. 6 shows a block diagram 600 of a wireless device 605 that supportssearch space configurations for RACH messaging in accordance withaspects of the present disclosure. Wireless device 605 may be an exampleof aspects of UE 115 as described herein. Wireless device 605 mayinclude receiver 610, UE search space module 615, and transmitter 620.Wireless device 605 may also include a processor. Each of thesecomponents may be in communication with one another (e.g., via one ormore buses).

Receiver 610 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to search spaceconfigurations for RACH messaging, etc.). Information may be passed onto other components of the device. The receiver 610 may be an example ofaspects of the transceiver 935 described with reference to FIG. 9. Thereceiver 610 may utilize a single antenna or a set of antennas.

UE search space module 615 may be an example of aspects of the UE searchspace module 915 described with reference to FIG. 9.

UE search space module 615 and/or at least some of its varioussub-components may be implemented in hardware, software executed by aprocessor, firmware, or any combination thereof. If implemented insoftware executed by a processor, the functions of the UE search spacemodule 615 and/or at least some of its various sub-components may beexecuted by a general-purpose processor, a digital signal processor(DSP), an application-specific integrated circuit (ASIC), anfield-programmable gate array (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware components,or any combination thereof designed to perform the functions describedin the present disclosure. The UE search space module 615 and/or atleast some of its various sub-components may be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations by one or morephysical devices. In some examples, UE search space module 615 and/or atleast some of its various sub-components may be a separate and distinctcomponent in accordance with various aspects of the present disclosure.In other examples, UE search space module 615 and/or at least some ofits various sub-components may be combined with one or more otherhardware components, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

UE search space module 615 may transmit, to a base station, a first RACHmessage based on an SSB received by the UE on a first receive beam,identify a set of time resources used by the base station fortransmission of one or more other SSBs from the base station, identify asearch space for receiving a PDCCH message based on the first RACHmessage, where the identified search space includes time resources thatare different from the identified set of time resources, and monitor forthe PDCCH message in the identified search space.

Transmitter 620 may transmit signals generated by other components ofthe device. In some examples, the transmitter 620 may be collocated witha receiver 610 in a transceiver module. For example, the transmitter 620may be an example of aspects of the transceiver 935 described withreference to FIG. 9. The transmitter 620 may utilize a single antenna ora set of antennas.

FIG. 7 shows a block diagram 700 of a wireless device 705 that supportssearch space configurations for RACH messaging in accordance withaspects of the present disclosure. Wireless device 705 may be an exampleof aspects of a wireless device 605 or a UE 115 as described withreference to FIG. 6. Wireless device 705 may include receiver 710, UEsearch space module 715, and transmitter 720. Wireless device 705 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 710 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to search spaceconfigurations for RACH messaging, etc.). Information may be passed onto other components of the device. The receiver 710 may be an example ofaspects of the transceiver 935 described with reference to FIG. 9. Thereceiver 710 may utilize a single antenna or a set of antennas.

UE search space module 715 may be an example of aspects of the UE searchspace module 915 described with reference to FIG. 9. UE search spacemodule 715 may also include transmission component 725, time resourceidentifier 730, search space identifier 735, and monitoring component740.

Transmission component 725 may transmit, to a base station, a first RACHmessage based on an SSB received by the UE on a first receive beam. Timeresource identifier 730 may identify a set of time resources used by thebase station for transmission of one or more other SSBs from the basestation. Search space identifier 735 may identify a search space forreceiving a PDCCH message based on the first RACH message, where theidentified search space includes time resources that are different fromthe identified set of time resources. Monitoring component 740 maymonitor for the PDCCH message in the identified search space.

Transmitter 720 may transmit signals generated by other components ofthe device. In some examples, the transmitter 720 may be collocated witha receiver 710 in a transceiver module. For example, the transmitter 720may be an example of aspects of the transceiver 935 described withreference to FIG. 9. The transmitter 720 may utilize a single antenna ora set of antennas.

FIG. 8 shows a block diagram 800 of a UE search space module 815 thatsupports search space configurations for RACH messaging in accordancewith aspects of the present disclosure. The UE search space module 815may be an example of aspects of a UE search space module 615, a UEsearch space module 715, or a UE search space module 915 described withreference to FIGS. 6, 7, and 9. The UE search space module 815 mayinclude transmission component 820, time resource identifier 825, searchspace identifier 830, monitoring component 835, search spaceconfiguration component 840, reception component 845, and beam selectioncomponent 850. Each of these modules may communicate, directly orindirectly, with one another (e.g., via one or more buses).

Transmission component 820 may transmit, to a base station, a first RACHmessage based on an SSB received by a UE 115 on a first receive beam.

Time resource identifier 825 may identify a set of time resources usedby the base station for transmission of one or more other SSBs from thebase station. In some cases, the one or more other SSBs are received bya UE 115 on receive beams that are different from the first receivebeam. In some cases, the one or more other SSBs are examples of one ormore SSBs actually transmitted by the base station. In some cases, timeresource identifier 825 may receive, from the base station, anindication of the one or more SSBs actually transmitted by the basestation in RMSI, other system information (OSI), an RRC message, a MACCE, a handover message, or a combination thereof. In some cases,locations of the one or more other SSBs are fixed.

Search space identifier 830 may identify a search space for receiving aPDCCH message based on the first RACH message, where the identifiedsearch space includes time resources that are different from theidentified set of time resources. In some cases, search space identifier830 may identify an RMSI search space corresponding to the SSB andconfigured via a PBCH configuration, where identifying the search spacemay further include removing time resources from the identified RMSIsearch space that overlap with the identified set of time resources,where the identified search space includes remaining time resources ofthe identified RMSI search space. In some cases, removing the timeresources from the identified RMSI search space includes altering aslot-level periodicity of the identified RMSI search space, where theidentified search space includes same symbol index locations as theidentified RMSI search space but with the altered slot-level periodicityof the identified RMSI search space. In some cases, identifying thesearch space may further include determining to implement a defaultsearch space based on an RMSI transmission from the base station, andidentifying monitoring occasions for monitoring for the PDCCH messagebased on monitoring occasions of the RMSI search space. In some cases,identifying the search space may further include identifying an RMSIsearch space with time resources non-overlapping with the identified setof time resources, where the identified search space includes theidentified RMSI search space. In some cases, identifying the searchspace may further include identifying a start of the search space basedon transmitting the first RACH message, and identifying an end of thesearch space based on a response timer. In some cases, the responsetimer includes a RAR window, a contention resolution timer, or acombination thereof.

Monitoring component 835 may monitor for the PDCCH message in theidentified search space. In some cases, beam selection component 850 mayselect the first receive beam, where the identified search space ismonitored using the selected first receive beam during the timeresources that are different from the identified set of time resources.In some cases, beam selection component 850 may additionally select asecond receive beam different from the selected first receive beam.Monitoring component 835 may monitor for at least one SSB of the one ormore other SSBs using the selected second receive beam during theidentified set of time resources. In some cases, the PDCCH message is anexample of a PDCCH grant for a RACH Msg2 transmission, a PDCCH grant fora RACH Msg3 transmission, a PDCCH grant for a RACH Msg4 transmission, ora combination thereof.

Search space configuration component 840 may receive, from the basestation, an indication of a set of time resources for the search space,and may remove time resources of the identified set of time resourcesfrom the indicated set of time resources for the search space, where theidentified search space includes remaining time resources of theindicated set of time resources for the search space. In some cases, theindication of the set of time resources for the search space includes atime window for the search space. In some cases, a subset of slots ofthe time window include the identified search space. In some cases, thesubset of slots includes each slot of the time window.

In some cases, reception component 845 may receive the SSB from the basestation, where the first RACH message is transmitted in a RACH occasioncorresponding to the SSB. Additionally or alternatively, receptioncomponent 845 may receive the at least one SSB of the one or more otherSSBs from the base station based on the time resources for theidentified search space not overlapping with the identified set of timeresources. In some cases, reception component 845 may receive the PDCCHmessage in CCEs of the identified search space based on the monitoring.

FIG. 9 illustrates a block diagram of a system 900 including a device905 that supports search space configurations for RACH messaging inaccordance with aspects of the present disclosure. Device 905 may be anexample of or include the components of wireless device 605, wirelessdevice 705, or a UE 115 as described herein, e.g., with reference toFIGS. 6 and 7. Device 905 may include components for bi-directionalvoice and data communications including components for transmitting andreceiving communications, including UE search space module 915,processor 920, memory 925, software 930, transceiver 935, antenna 940,and I/O controller 945. These components may be in electroniccommunication via one or more buses (e.g., bus 910). Device 905 maycommunicate wirelessly with one or more base stations 105.

Processor 920 may include an intelligent hardware device (e.g., ageneral-purpose processor, a DSP, a central processing unit (CPU), amicrocontroller, an ASIC, an FPGA, a PLD, a discrete gate or transistorlogic component, a discrete hardware component, or any combinationthereof). In some cases, processor 920 may be configured to operate amemory array using a memory controller. In other cases, a memorycontroller may be integrated into processor 920. Processor 920 may beconfigured to execute computer-readable instructions stored in a memoryto perform various functions (e.g., functions or tasks supporting searchspace configurations for RACH messaging).

Memory 925 may include random-access memory (RAM) and read-only memory(ROM). The memory 925 may store computer-readable, computer-executablesoftware 930 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 925 may contain, among other things, a basic I/O system(BIOS) which may control basic hardware or software operation such asthe interaction with peripheral components or devices.

Software 930 may include code to implement aspects of the presentdisclosure, including code to support search space configurations forRACH messaging. Software 930 may be stored in a non-transitorycomputer-readable medium such as system memory or other memory. In somecases, the software 930 may not be directly executable by the processorbut may cause a computer (e.g., when compiled and executed) to performfunctions described herein.

Transceiver 935 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 935 may represent a wireless transceiver and may communicatebi-directionally with another wireless transceiver. The transceiver 935may also include a modem to modulate the packets and provide themodulated packets to the antennas for transmission, and to demodulatepackets received from the antennas.

In some cases, the wireless device may include a single antenna 940.However, in some cases the device may have more than one antenna 940,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

I/O controller 945 may manage input and output signals for device 905.I/O controller 945 may also manage peripherals not integrated intodevice 905. In some cases, I/O controller 945 may represent a physicalconnection or port to an external peripheral. In some cases, I/Ocontroller 945 may utilize an operating system such as iOS®, ANDROID®,MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operatingsystem. In other cases, I/O controller 945 may represent or interactwith a modem, a keyboard, a mouse, a touchscreen, or a similar device.In some cases, I/O controller 945 may be implemented as part of aprocessor. In some cases, a user may interact with device 905 via I/Ocontroller 945 or via hardware components controlled by I/O controller945.

FIG. 10 shows a block diagram 1000 of a wireless device 1005 thatsupports search space configurations for RACH messaging in accordancewith aspects of the present disclosure. Wireless device 1005 may be anexample of aspects of a base station 105 as described herein. Wirelessdevice 1005 may include receiver 1010, base station search space module1015, and transmitter 1020. Wireless device 1005 may also include aprocessor. Each of these components may be in communication with oneanother (e.g., via one or more buses).

Receiver 1010 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to search spaceconfigurations for RACH messaging, etc.). Information may be passed onto other components of the device. The receiver 1010 may be an exampleof aspects of the transceiver 1335 described with reference to FIG. 13.The receiver 1010 may utilize a single antenna or a set of antennas.

Base station search space module 1015 may be an example of aspects ofthe base station search space module 1315 described with reference toFIG. 13.

Base station search space module 1015 and/or at least some of itsvarious sub-components may be implemented in hardware, software executedby a processor, firmware, or any combination thereof. If implemented insoftware executed by a processor, the functions of the base stationsearch space module 1015 and/or at least some of its varioussub-components may be executed by a general-purpose processor, a DSP, anASIC, an FPGA or other PLD, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure. The base station searchspace module 1015 and/or at least some of its various sub-components maybe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical devices. In some examples, basestation search space module 1015 and/or at least some of its varioussub-components may be a separate and distinct component in accordancewith various aspects of the present disclosure. In other examples, basestation search space module 1015 and/or at least some of its varioussub-components may be combined with one or more other hardwarecomponents, including but not limited to an I/O component, atransceiver, a network server, another computing device, one or moreother components described in the present disclosure, or a combinationthereof in accordance with various aspects of the present disclosure.

Base station search space module 1015 may receive, from a UE 115, afirst RACH message based on an SSB received by the UE 115 on a firstreceive beam, identify a set of time resources used for transmission ofone or more other SSBs by the base station, and identify a search spacefor the UE 115 to receive a PDCCH message based on the first RACHmessage, where the identified search space includes time resources thatare different from the identified set of time resources. Base stationsearch space module 1015 may additionally map the PDCCH message to CCEswithin the identified search space, and transmit, to the UE, the PDCCHmessage according to the mapping.

Transmitter 1020 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1020 may be collocatedwith a receiver 1010 in a transceiver module. For example, thetransmitter 1020 may be an example of aspects of the transceiver 1335described with reference to FIG. 13. The transmitter 1020 may utilize asingle antenna or a set of antennas.

FIG. 11 shows a block diagram 1100 of a wireless device 1105 thatsupports search space configurations for RACH messaging in accordancewith aspects of the present disclosure. Wireless device 1105 may be anexample of aspects of a wireless device 1005 or a base station 105 asdescribed with reference to FIG. 10. Wireless device 1105 may includereceiver 1110, base station search space module 1115, and transmitter1120. Wireless device 1105 may also include a processor. Each of thesecomponents may be in communication with one another (e.g., via one ormore buses).

Receiver 1110 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to search spaceconfigurations for RACH messaging, etc.). Information may be passed onto other components of the device. The receiver 1110 may be an exampleof aspects of the transceiver 1335 described with reference to FIG. 13.The receiver 1110 may utilize a single antenna or a set of antennas.

Base station search space module 1115 may be an example of aspects ofthe base station search space module 1315 described with reference toFIG. 13. Base station search space module 1115 may also includereception component 1125, time resource identifier 1130, search spaceidentifier 1135, mapping component 1140, and transmission component1145.

Reception component 1125 may receive, from a UE, a first RACH messagebased on an SSB received by a UE 115 on a first receive beam. Timeresource identifier 1130 may identify a set of time resources used fortransmission of one or more other SSBs by the base station. In somecases, the one or more other SSBs are received by the UE 115 on receivebeams that are different from the first receive beam. Search spaceidentifier 1135 may identify a search space for the UE 115 to receive aPDCCH message based on the first RACH message, where the identifiedsearch space includes time resources that are different from theidentified set of time resources. Mapping component 1140 may map thePDCCH message to CCEs within the identified search space. Transmissioncomponent 1145 may transmit, to the UE, the PDCCH message according tothe mapping.

Transmitter 1120 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1120 may be collocatedwith a receiver 1110 in a transceiver module. For example, thetransmitter 1120 may be an example of aspects of the transceiver 1335described with reference to FIG. 13. The transmitter 1120 may utilize asingle antenna or a set of antennas.

FIG. 12 shows a block diagram 1200 of a base station search space module1215 that supports search space configurations for RACH messaging inaccordance with aspects of the present disclosure. The base stationsearch space module 1215 may be an example of aspects of a base stationsearch space module 1315 described with reference to FIGS. 10, 11, and13. The base station search space module 1215 may include receptioncomponent 1220, time resource identifier 1225, search space identifier1230, mapping component 1235, transmission component 1240, and searchspace configuration component 1245. Each of these modules maycommunicate, directly or indirectly, with one another (e.g., via one ormore buses).

Reception component 1220 may receive, from a UE, a first RACH messagebased on an SSB received by the UE 115 on a first receive beam.

Time resource identifier 1225 may identify a set of time resources usedfor transmission of one or more other SSBs by the base station. In somecases, the one or more other SSBs are received by a UE 115 on receivebeams that are different from the first receive beam.

Search space identifier 1230 may identify a search space for a UE 115 toreceive a PDCCH message based on the first RACH message, where theidentified search space includes time resources that are different fromthe identified set of time resources. In some cases, search spaceidentifier 1230 may identify an RMSI search space corresponding to theSSB and configured via a PBCH configuration. In some cases, identifyingthe search space further includes removing time resources from theidentified RMSI search space that overlap with the identified set oftime resources, where the identified search space includes remainingtime resources of the identified RMSI search space. In some cases,removing the time resources for the identified RMSI search spaceincludes altering a slot-level periodicity of the identified RMSI searchspace, where the identified search space includes same symbol indexlocations as the identified RMSI search space but with the alteredslot-level periodicity of the identified RMSI search space. In othercases, identifying the search space further includes identifying an RMSIsearch space with time resources non-overlapping with the identified setof time resources, where the identified search space includes theidentified RMSI search space.

Mapping component 1235 may map the PDCCH message to CCEs within theidentified search space.

Transmission component 1240 may transmit, to the UE, the PDCCH messageaccording to the mapping. In some cases, transmission component 1240 maytransmit, to the UE, the SSB, where the first RACH message is receivedin a RACH occasion corresponding to the SSB. In some cases, the PDCCHmessage is an example of a PDCCH grant for a RACH Msg2 transmission, aPDCCH grant for a RACH Msg3 transmission, a PDCCH grant for a RACH Msg4transmission, or a combination thereof.

Search space configuration component 1245 may transmit, to the UE, anindication of a set of time resources for the search space, and mayremove time resources of the identified set of time resources from theindicated set of time resources for the search space, where theidentified search space includes remaining time resources of theindicated set of time resources for the search space. In some cases, theindication of the set of time resources for the search space includes atime window for the search space. In some cases, a subset of slots ofthe time window include the identified search space. In some cases, thesubset of slots includes each slot of the time window.

FIG. 13 illustrates a block diagram of a system 1300 including a device1305 that supports search space configurations for RACH messaging inaccordance with aspects of the present disclosure. Device 1305 may be anexample of or include the components of base station 105 as describedherein, e.g., with reference to FIG. 1. Device 1305 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including basestation search space module 1315, processor 1320, memory 1325, software1330, transceiver 1335, antenna 1340, network communications manager1345, and inter-station communications manager 1350. These componentsmay be in electronic communication via one or more buses (e.g., bus1310). Device 1305 may communicate wirelessly with one or more UEs 115.

Processor 1320 may include an intelligent hardware device (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a PLD, a discrete gate or transistor logic component, a discretehardware component, or any combination thereof). In some cases,processor 1320 may be configured to operate a memory array using amemory controller. In other cases, a memory controller may be integratedinto processor 1320. Processor 1320 may be configured to executecomputer-readable instructions stored in a memory to perform variousfunctions (e.g., functions or tasks supporting search spaceconfigurations for RACH messaging).

Memory 1325 may include RAM and ROM. The memory 1325 may storecomputer-readable, computer-executable software 1330 includinginstructions that, when executed, cause the processor to perform variousfunctions described herein. In some cases, the memory 1325 may contain,among other things, a BIOS which may control basic hardware or softwareoperation such as the interaction with peripheral components or devices.

Software 1330 may include code to implement aspects of the presentdisclosure, including code to support search space configurations forRACH messaging. Software 1330 may be stored in a non-transitorycomputer-readable medium such as system memory or other memory. In somecases, the software 1330 may not be directly executable by the processorbut may cause a computer (e.g., when compiled and executed) to performfunctions described herein.

Transceiver 1335 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 1335 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1335 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1340.However, in some cases the device may have more than one antenna 1340,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

Network communications manager 1345 may manage communications with thecore network 130 (e.g., via one or more wired backhaul links). Forexample, the network communications manager 1345 may manage the transferof data communications for client devices, such as one or more UEs 115.

Inter-station communications manager 1350 may manage communications withother base station 105, and may include a controller or scheduler forcontrolling communications with UEs 115 in cooperation with other basestations 105. For example, the inter-station communications manager 1350may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, inter-station communications manager1350 may provide an X2 interface within an LTE/LTE-A wirelesscommunication network technology to provide communication between basestations 105.

FIG. 14 shows a flowchart illustrating a method 1400 for search spaceconfigurations for RACH messaging in accordance with aspects of thepresent disclosure. The operations of method 1400 may be implemented bya UE 115 or its components as described herein. For example, theoperations of method 1400 may be performed by a UE search space moduleas described with reference to FIGS. 6 through 9. In some examples, a UE115 may execute a set of codes to control the functional elements of thedevice to perform the functions described herein. Additionally oralternatively, the UE 115 may perform aspects of the functions describedherein using special-purpose hardware.

At 1405 the UE 115 may transmit, to a base station, a first RACH messagebased on an SSB received by the UE 115 on a first receive beam. Theoperations of 1405 may be performed according to the methods describedherein. In certain examples, aspects of the operations of 1405 may beperformed by a transmission component as described with reference toFIGS. 6 through 9.

At 1410 the UE 115 may identify a set of time resources used by the basestation for transmission of one or more other SSBs from the basestation. The operations of 1410 may be performed according to themethods described herein. In certain examples, aspects of the operationsof 1410 may be performed by a time resource identifier as described withreference to FIGS. 6 through 9.

At 1415 the UE 115 may identify a search space for receiving a PDCCHmessage based on the first RACH message, where the identified searchspace includes time resources that are different from the identified setof time resources. The operations of 1415 may be performed according tothe methods described herein. In certain examples, aspects of theoperations of 1415 may be performed by a search space identifier asdescribed with reference to FIGS. 6 through 9.

At 1420 the UE 115 may monitor for the PDCCH message in the identifiedsearch space. The operations of 1420 may be performed according to themethods described herein. In certain examples, aspects of the operationsof 1420 may be performed by a monitoring component as described withreference to FIGS. 6 through 9.

FIG. 15 shows a flowchart illustrating a method 1500 for search spaceconfigurations for RACH messaging in accordance with aspects of thepresent disclosure. The operations of method 1500 may be implemented bya UE 115 or its components as described herein. For example, theoperations of method 1500 may be performed by a UE search space moduleas described with reference to FIGS. 6 through 9. In some examples, a UE115 may execute a set of codes to control the functional elements of thedevice to perform the functions described herein. Additionally oralternatively, the UE 115 may perform aspects of the functions describedherein using special-purpose hardware.

At 1505 the UE 115 may transmit, to a base station, a first RACH messagebased on an SSB received by the UE 115 on a first receive beam. Theoperations of 1505 may be performed according to the methods describedherein. In certain examples, aspects of the operations of 1505 may beperformed by a transmission component as described with reference toFIGS. 6 through 9.

At 1510 the UE 115 may identify a set of time resources used by the basestation for transmission of one or more other SSBs from the basestation. The operations of 1510 may be performed according to themethods described herein. In certain examples, aspects of the operationsof 1510 may be performed by a time resource identifier as described withreference to FIGS. 6 through 9.

At 1515 the UE 115 may identify a search space for receiving a PDCCHmessage based on the first RACH message, where the identified searchspace includes time resources that are different from the identified setof time resources. The operations of 1515 may be performed according tothe methods described herein. In certain examples, aspects of theoperations of 1515 may be performed by a search space identifier asdescribed with reference to FIGS. 6 through 9.

At 1520 the UE 115 may select the first receive beam. The operations of1520 may be performed according to the methods described herein. Incertain examples, aspects of the operations of 1520 may be performed bya beam selection component as described with reference to FIGS. 6through 9.

At 1525 the UE 115 may monitor for the PDCCH message in the identifiedsearch space, where the identified search space is monitored using theselected first receive beam during the time resources that are differentfrom the identified set of time resources. The operations of 1525 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of 1525 may be performed by amonitoring component as described with reference to FIGS. 6 through 9.

At 1530 the UE 115 may select a second receive beam different from theselected first receive beam. The operations of 1530 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of 1530 may be performed by a beam selection componentas described with reference to FIGS. 6 through 9.

At 1535 the UE 115 may monitor for at least one SSB of the one or moreother SSBs using the selected second receive beam during the identifiedset of time resources. The operations of 1535 may be performed accordingto the methods described herein. In certain examples, aspects of theoperations of 1535 may be performed by a monitoring component asdescribed with reference to FIGS. 6 through 9.

FIG. 16 shows a flowchart illustrating a method 1600 for search spaceconfigurations for RACH messaging in accordance with aspects of thepresent disclosure. The operations of method 1600 may be implemented bya base station 105 or its components as described herein. For example,the operations of method 1600 may be performed by a base station searchspace module as described with reference to FIGS. 10 through 13. In someexamples, a base station 105 may execute a set of codes to control thefunctional elements of the device to perform the functions describedherein. Additionally or alternatively, the base station 105 may performaspects of the functions described herein using special-purposehardware.

At 1605 the base station 105 may receive, from a UE 115, a first RACHmessage based on an SSB received by the UE 115 on a first receive beam.The operations of 1605 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations of 1605may be performed by a reception component as described with reference toFIGS. 10 through 13.

At 1610 the base station 105 may identify a set of time resources usedfor transmission of one or more other SSBs by the base station 105. Theoperations of 1610 may be performed according to the methods describedherein. In certain examples, aspects of the operations of 1610 may beperformed by a time resource identifier as described with reference toFIGS. 10 through 13.

At 1615 the base station 105 may identify a search space for the UE 115to receive a PDCCH message based on the first RACH message, where theidentified search space includes time resources that are different fromthe identified set of time resources. The operations of 1615 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of 1615 may be performed by a searchspace identifier as described with reference to FIGS. 10 through 13.

At 1620 the base station 105 may map the PDCCH message to CCEs withinthe identified search space. The operations of 1620 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of 1620 may be performed by a mapping component asdescribed with reference to FIGS. 10 through 13.

At 1625 the base station 105 may transmit, to the UE 115, the PDCCHmessage according to the mapping. The operations of 1625 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of 1625 may be performed by atransmission component as described with reference to FIGS. 10 through13.

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), E-UTRA, Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned herein as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEs115 with service subscriptions with the network provider. A small cellmay be associated with a lower-powered base station 105, as comparedwith a macro cell, and a small cell may operate in the same or different(e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Smallcells may include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs 115 with servicesubscriptions with the network provider. A femto cell may also cover asmall geographic area (e.g., a home) and may provide restricted accessby UEs 115 having an association with the femto cell (e.g., UEs 115 in aclosed subscriber group (CSG), UEs 115 for users in the home, and thelike). An eNB for a macro cell may be referred to as a macro eNB. An eNBfor a small cell may be referred to as a small cell eNB, a pico eNB, afemto eNB, or a home eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells, and may also support communicationsusing one or multiple CCs.

The wireless communications system 100 or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations 105 may have similar frame timing, andtransmissions from different base stations 105 may be approximatelyaligned in time. For asynchronous operation, the base stations 105 mayhave different frame timing, and transmissions from different basestations 105 may not be aligned in time. The techniques described hereinmay be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other PLD,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude RAM, ROM, electrically erasable programmable read only memory(EEPROM), flash memory, compact disk (CD) ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother non-transitory medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communications at a userequipment (UE), comprising: transmitting, to a base station, a firstrandom access (RACH) message based at least in part on a synchronizationsignal block (SSB) received by the UE on a first receive beam;identifying a set of time resources used by the base station fortransmission of one or more other SSBs from the base station;identifying a search space for receiving a physical downlink controlchannel (PDCCH) message based at least in part on the first RACHmessage, wherein the identified search space comprises time resourcesthat are different from the identified set of time resources; andmonitoring for the PDCCH message in the identified search space.
 2. Themethod of claim 1, wherein the PDCCH message comprises a PDCCH grant fora RACH message 2 (Msg2) transmission, a PDCCH grant for a RACH message 3(Msg3) transmission, a PDCCH grant for a RACH message 4 (Msg4)transmission, or a combination thereof.
 3. The method of claim 1,wherein the one or more other SSBs are received by the UE on receivebeams that are different from the first receive beam.
 4. The method ofclaim 1, further comprising: identifying a remaining minimum systeminformation (RMSI) search space corresponding to the SSB and configuredvia a physical broadcast channel (PBCH) configuration.
 5. The method ofclaim 4, wherein identifying the search space further comprises:removing time resources from the identified RMSI search space thatoverlap with the identified set of time resources, wherein theidentified search space comprises remaining time resources of theidentified RMSI search space.
 6. The method of claim 5, wherein removingthe time resources for the identified RMSI search space comprises:altering a slot-level periodicity of the identified RMSI search space,wherein the identified search space comprises same symbol indexlocations as the identified RMSI search space but with the alteredslot-level periodicity of the identified RMSI search space.
 7. Themethod of claim 4, wherein identifying the search space furthercomprises: determining to implement a default search space based atleast in part on an RMSI transmission from the base station; andidentifying monitoring occasions for monitoring for the PDCCH messagebased at least in part on monitoring occasions of the RMSI search space.8. The method of claim 1, wherein identifying the search space furthercomprises: identifying a remaining minimum system information (RMSI)search space with time resources non-overlapping with the identified setof time resources, wherein the identified search space comprises theidentified RMSI search space.
 9. The method of claim 1, furthercomprising: receiving, from the base station, an indication of a set oftime resources for the search space; and removing time resources of theidentified set of time resources from the indicated set of timeresources for the search space, wherein the identified search spacecomprises remaining time resources of the indicated set of timeresources for the search space.
 10. The method of claim 9, wherein: theindication of the set of time resources for the search space comprises atime window for the search space; and a subset of slots of the timewindow comprise the identified search space.
 11. The method of claim 10,wherein the subset of slots comprises each slot of the time window. 12.The method of claim 1, wherein identifying the search space furthercomprises: identifying a start of the search space based at least inpart on transmitting the first RACH message; and identifying an end ofthe search space based at least in part on a response timer.
 13. Themethod of claim 12, wherein the response timer comprises a random accessresponse (RAR) window, a contention resolution timer, or a combinationthereof.
 14. The method of claim 1, further comprising: receiving theSSB from the base station, wherein the first RACH message is transmittedin a RACH occasion corresponding to the SSB.
 15. The method of claim 1,further comprising: selecting the first receive beam, wherein theidentified search space is monitored using the selected first receivebeam during the time resources that are different from the identifiedset of time resources; selecting a second receive beam different fromthe selected first receive beam; and monitoring for at least one SSB ofthe one or more other SSBs using the selected second receive beam duringthe identified set of time resources.
 16. The method of claim 15,further comprising: receiving the at least one SSB of the one or moreother SSBs from the base station based at least in part on the timeresources for the identified search space not overlapping with theidentified set of time resources.
 17. The method of claim 1, furthercomprising: receiving the PDCCH message in control channel elements(CCEs) of the identified search space based at least in part on themonitoring.
 18. The method of claim 1, wherein the one or more otherSSBs comprise one or more SSBs actually transmitted by the base station.19. The method of claim 18, further comprising: receiving, from the basestation, an indication of the one or more SSBs actually transmitted bythe base station in remaining minimum system information (RMSI), othersystem information (OSI), a radio resource control (RRC) message, amedium access control (MAC) control element (CE), a handover message, ora combination thereof.
 20. The method of claim 1, wherein locations ofthe one or more other SSBs are fixed.
 21. A method for wirelesscommunications at a base station, comprising: receiving, from a userequipment (UE), a first random access (RACH) message based at least inpart on a synchronization signal block (SSB) received by the UE on afirst receive beam; identifying a set of time resources used fortransmission of one or more other SSBs by the base station; identifyinga search space for the UE to receive a physical downlink control channel(PDCCH) message based at least in part on the first RACH message,wherein the identified search space comprises time resources that aredifferent from the identified set of time resources; mapping the PDCCHmessage to control channel elements (CCEs) within the identified searchspace; and transmitting, to the UE, the PDCCH message according to themapping.
 22. The method of claim 21, wherein the PDCCH message comprisesa PDCCH grant for a RACH message 2 (Msg2) transmission, a PDCCH grantfor a RACH message 3 (Msg3) transmission, a PDCCH grant for a RACHmessage 4 (Msg4) transmission, or a combination thereof.
 23. The methodof claim 21, wherein the one or more other SSBs are received by the UEon receive beams that are different from the first receive beam.
 24. Themethod of claim 21, further comprising: identifying a remaining minimumsystem information (RMSI) search space corresponding to the SSB andconfigured via a physical broadcast channel (PBCH) configuration. 25.The method of claim 24, wherein identifying the search space furthercomprises: removing time resources from the identified RMSI search spacethat overlap with the identified set of time resources, wherein theidentified search space comprises remaining time resources of theidentified RMSI search space.
 26. The method of claim 25, whereinremoving the time resources for the identified RMSI search spacecomprises: altering a slot-level periodicity of the identified RMSIsearch space, wherein the identified search space comprises same symbolindex locations as the identified RMSI search space but with the alteredslot-level periodicity of the identified RMSI search space.
 27. Themethod of claim 21, wherein identifying the search space furthercomprises: identifying a remaining minimum system information (RMSI)search space with time resources non-overlapping with the identified setof time resources, wherein the identified search space comprises theidentified RMSI search space.
 28. The method of claim 21, furthercomprising: transmitting, to the UE, an indication of a set of timeresources for the search space; and removing time resources of theidentified set of time resources from the indicated set of timeresources for the search space, wherein the identified search spacecomprises remaining time resources of the indicated set of timeresources for the search space.
 29. The method of claim 28, wherein: theindication of the set of time resources for the search space comprises atime window for the search space; and a subset of slots of the timewindow comprise the identified search space.
 30. The method of claim 29,wherein the subset of slots comprises each slot of the time window. 31.The method of claim 21, further comprising: transmitting, to the UE, theSSB, wherein the first RACH message is received in a RACH occasioncorresponding to the SSB.
 32. An apparatus for wireless communicationsat a user equipment (UE), comprising: means for transmitting, to a basestation, a first random access (RACH) message based at least in part ona synchronization signal block (SSB) received by the UE on a firstreceive beam; means for identifying a set of time resources used by thebase station for transmission of one or more other SSBs from the basestation; means for identifying a search space for receiving a physicaldownlink control channel (PDCCH) message based at least in part on thefirst RACH message, wherein the identified search space comprises timeresources that are different from the identified set of time resources;and means for monitoring for the PDCCH message in the identified searchspace.
 33. An apparatus for wireless communications at a base station,comprising: means for receiving, from a user equipment (UE), a firstrandom access (RACH) message based at least in part on a synchronizationsignal block (SSB) received by the UE on a first receive beam; means foridentifying a set of time resources used for transmission of one or moreother SSBs by the base station; means for identifying a search space forthe UE to receive a physical downlink control channel (PDCCH) messagebased at least in part on the first RACH message, wherein the identifiedsearch space comprises time resources that are different from theidentified set of time resources; means for mapping the PDCCH message tocontrol channel elements (CCEs) within the identified search space; andmeans for transmitting, to the UE, the PDCCH message according to themapping.
 34. An apparatus for wireless communications at a userequipment (UE), comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memoryand executable by the processor to cause the apparatus to: transmit, toa base station, a first random access (RACH) message based at least inpart on a synchronization signal block (SSB) received by the UE on afirst receive beam; identify a set of time resources used by the basestation for transmission of one or more other SSBs from the basestation; identify a search space for receiving a physical downlinkcontrol channel (PDCCH) message based at least in part on the first RACHmessage, wherein the identified search space comprises time resourcesthat are different from the identified set of time resources; andmonitor for the PDCCH message in the identified search space.
 35. Theapparatus of claim 34, wherein the PDCCH message comprises a PDCCH grantfor a RACH message 2 (Msg2) transmission, a PDCCH grant for a RACHmessage 3 (Msg3) transmission, a PDCCH grant for a RACH message 4 (Msg4)transmission, or a combination thereof.
 36. The apparatus of claim 34,wherein the one or more other SSBs are received by the UE on receivebeams that are different from the first receive beam.
 37. The apparatusof claim 34, wherein the instructions are further executable by theprocessor to cause the apparatus to: identify a remaining minimum systeminformation (RMSI) search space corresponding to the SSB and configuredvia a physical broadcast channel (PBCH) configuration.
 38. The apparatusof claim 37, wherein the instructions to identify the search spacefurther are executable by the processor to cause the apparatus to:remove time resources from the identified RMSI search space that overlapwith the identified set of time resources, wherein the identified searchspace comprises remaining time resources of the identified RMSI searchspace.
 39. The apparatus of claim 38, wherein the instructions to removethe time resources for the identified RMSI search space are executableby the processor to cause the apparatus to: alter a slot-levelperiodicity of the identified RMSI search space, wherein the identifiedsearch space comprises same symbol index locations as the identifiedRMSI search space but with the altered slot-level periodicity of theidentified RMSI search space.
 40. The apparatus of claim 37, wherein theinstructions to identify the search space further are executable by theprocessor to cause the apparatus to: determine to implement a defaultsearch space based at least in part on an RMSI transmission from thebase station; and identify monitoring occasions for monitoring for thePDCCH message based at least in part on monitoring occasions of the RMSIsearch space.
 41. The apparatus of claim 34, wherein the instructions toidentify the search space further are executable by the processor tocause the apparatus to: identify a remaining minimum system information(RMSI) search space with time resources non-overlapping with theidentified set of time resources, wherein the identified search spacecomprises the identified RMSI search space.
 42. The apparatus of claim34, wherein the instructions are further executable by the processor tocause the apparatus to: receive, from the base station, an indication ofa set of time resources for the search space; and remove time resourcesof the identified set of time resources from the indicated set of timeresources for the search space, wherein the identified search spacecomprises remaining time resources of the indicated set of timeresources for the search space.
 43. The apparatus of claim 42, wherein:the indication of the set of time resources for the search spacecomprises a time window for the search space; and a subset of slots ofthe time window comprise the identified search space.
 44. The apparatusof claim 43, wherein the subset of slots comprises each slot of the timewindow.
 45. The apparatus of claim 34, wherein the instructions toidentify the search space further are executable by the processor tocause the apparatus to: identify a start of the search space based atleast in part on transmitting the first RACH message; and identify anend of the search space based at least in part on a response timer. 46.The apparatus of claim 45, wherein the response timer comprises a randomaccess response (RAR) window, a contention resolution timer, or acombination thereof.
 47. The apparatus of claim 34, wherein theinstructions are further executable by the processor to cause theapparatus to: receive the SSB from the base station, wherein the firstRACH message is transmitted in a RACH occasion corresponding to the SSB.48. The apparatus of claim 34, wherein the instructions are furtherexecutable by the processor to cause the apparatus to: select the firstreceive beam, wherein the identified search space is monitored using theselected first receive beam during the time resources that are differentfrom the identified set of time resources; select a second receive beamdifferent from the selected first receive beam; and monitor for at leastone SSB of the one or more other SSBs using the selected second receivebeam during the identified set of time resources.
 49. The apparatus ofclaim 48, wherein the instructions are further executable by theprocessor to cause the apparatus to: receive the at least one SSB of theone or more other SSBs from the base station based at least in part onthe time resources for the identified search space not overlapping withthe identified set of time resources.
 50. The apparatus of claim 34,wherein the instructions are further executable by the processor tocause the apparatus to: receive the PDCCH message in control channelelements (CCEs) of the identified search space based at least in part onthe monitoring.
 51. The apparatus of claim 34, wherein the one or moreother SSBs comprise one or more SSBs actually transmitted by the basestation.
 52. The apparatus of claim 51, wherein the instructions arefurther executable by the processor to cause the apparatus to: receive,from the base station, an indication of the one or more SSBs actuallytransmitted by the base station in remaining minimum system information(RMSI), other system information (OSI), a radio resource control (RRC)message, a medium access control (MAC) control element (CE), a handovermessage, or a combination thereof.
 53. The apparatus of claim 34,wherein locations of the one or more other SSBs are fixed.
 54. Anapparatus for wireless communications at a base station, comprising: aprocessor; memory in electronic communication with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to: receive, from a user equipment (UE), a firstrandom access (RACH) message based at least in part on a synchronizationsignal block (SSB) received by the UE on a first receive beam; identifya set of time resources used for transmission of one or more other SSBsby the base station; identify a search space for the UE to receive aphysical downlink control channel (PDCCH) message based at least in parton the first RACH message, wherein the identified search space comprisestime resources that are different from the identified set of timeresources; map the PDCCH message to control channel elements (CCEs)within the identified search space; and transmit, to the UE, the PDCCHmessage according to the mapping.
 55. The apparatus of claim 54, whereinthe PDCCH message comprises a PDCCH grant for a RACH message 2 (Msg2)transmission, a PDCCH grant for a RACH message 3 (Msg3) transmission, aPDCCH grant for a RACH message 4 (Msg4) transmission, or a combinationthereof.
 56. The apparatus of claim 54, wherein the one or more otherSSBs are received by the UE on receive beams that are different from thefirst receive beam.
 57. The apparatus of claim 54, wherein theinstructions are further executable by the processor to cause theapparatus to: identify a remaining minimum system information (RMSI)search space corresponding to the SSB and configured via a physicalbroadcast channel (PBCH) configuration.
 58. The apparatus of claim 57,wherein the instructions to identify the search space further areexecutable by the processor to cause the apparatus to: remove timeresources from the identified RMSI search space that overlap with theidentified set of time resources, wherein the identified search spacecomprises remaining time resources of the identified RMSI search space.59. The apparatus of claim 58, wherein the instructions to remove thetime resources for the identified RMSI search space are executable bythe processor to cause the apparatus to: alter a slot-level periodicityof the identified RMSI search space, wherein the identified search spacecomprises same symbol index locations as the identified RMSI searchspace but with the altered slot-level periodicity of the identified RMSIsearch space.
 60. The apparatus of claim 54, wherein the instructions toidentify the search space further are executable by the processor tocause the apparatus to: identify a remaining minimum system information(RMSI) search space with time resources non-overlapping with theidentified set of time resources, wherein the identified search spacecomprises the identified RMSI search space.
 61. The apparatus of claim54, wherein the instructions are further executable by the processor tocause the apparatus to: transmit, to the UE, an indication of a set oftime resources for the search space; and remove time resources of theidentified set of time resources from the indicated set of timeresources for the search space, wherein the identified search spacecomprises remaining time resources of the indicated set of timeresources for the search space.
 62. The apparatus of claim 61, wherein:the indication of the set of time resources for the search spacecomprises a time window for the search space; and a subset of slots ofthe time window comprise the identified search space.
 63. The apparatusof claim 62, wherein the subset of slots comprises each slot of the timewindow.
 64. The apparatus of claim 54, wherein the instructions arefurther executable by the processor to cause the apparatus to: transmit,to the UE, the SSB, wherein the first RACH message is received in a RACHoccasion corresponding to the SSB.
 65. A non-transitorycomputer-readable medium storing code for wireless communications at auser equipment (UE), the code comprising instructions executable by aprocessor to: transmit, to a base station, a first random access (RACH)message based at least in part on a synchronization signal block (SSB)received by the UE on a first receive beam; identify a set of timeresources used by the base station for transmission of one or more otherSSBs from the base station; identify a search space for receiving aphysical downlink control channel (PDCCH) message based at least in parton the first RACH message, wherein the identified search space comprisestime resources that are different from the identified set of timeresources; and monitor for the PDCCH message in the identified searchspace.
 66. A non-transitory computer-readable medium storing code forwireless communications at a base station, the code comprisinginstructions executable by a processor to: receive, from a userequipment (UE), a first random access (RACH) message based at least inpart on a synchronization signal block (SSB) received by the UE on afirst receive beam; identify a set of time resources used fortransmission of one or more other SSBs by the base station; identify asearch space for the UE to receive a physical downlink control channel(PDCCH) message based at least in part on the first RACH message,wherein the identified search space comprises time resources that aredifferent from the identified set of time resources; map the PDCCHmessage to control channel elements (CCEs) within the identified searchspace; and transmit, to the UE, the PDCCH message according to themapping.